Roy Diggle is an ex-military cop and a former NAVY SEAL who was under the wing of Richard Castle.
- Skilled Acrobat: Roy is quite skilled in gymnastics having trained in the sport since he was very young and made it to senior elite level. Roy showed he could easily scale a fence multiple meters high in one fluid movement, making use of a nearby wall to provide leverage.
- Intimidation: He leverages his considerable presence, his excellent training in psychology and interrogation, being obviously willing and able to hit people really really hard, suddenly shifting toward protectiveness, etc. to achieve remarkable results.
- Expert Spy: Roy was proven quite skillful in the act of espionage, spying on his enemies and allies alike just to keep tabs as well as confirm his suspicions.
- Extensive military training: Roy is well-trained in the armed forces disciplines, and has mentioned that he was once a part of Special Forces. He has considerable experience in live combat, having done three tours in Afghanistan.
- Expert Martial Artist: Roy also has extensive training in martial arts and unarmed combat, holding black belts in Judo, Kendo and Aikido. His level of skill is sufficient to defeat six normal men with his eyes closed, and he has in the past held his own against such dangerous enemies as Chase and Ayame.
- Expert hand-to-hand combatant:He is a skilled fighter, having developed his skills during his time as a soldier. He is skilled enough to match Dewei in combat and keep up with Richard during their sparring sessions. Roy was also able to hold his own against the highly skilled Jason, though he was supported by Dewei. However, he lost his fight against Chase, partially because Chase pulled two pistols on him. He has been increasing his skill in fighting as he regularly trains with Richard. Roy received basic training at West Point, then further, more intensive training in various martial arts during his travels around the world. Eva mentions that he uses at least three different fighting styles.
- Exceptional physical condition: Roy engages regularly in intense exercises and spars with Dewei during his spare time.
- Enhanced Conditioning: Roy further enhanced his overall conditioning by using a specific serum known as the "revelation serum" this serum has increased his overall physical and mental conditioning to nearly super human levels.
- Enhanced Strength: Roy is shown to be strong enough to lift a light platform, and can easily break bricks and concrete. Roy is shown to not have as much strength as Eric seeing as Eric easily overpowered his hand while they shook hands. However, Roy's strength is directly related to his base strength, that is, the stronger he gets on his own, his now enhanced strength will be exactly 4 (sometimes 5) times of that strength.
- Enhanced Durability: Roy is shown to be able to take a hit from a light platform, that was about to fall on Moira, he was able to punch through a brick wall without any visible damage to his hand.
- Enhanced Senses: Roy's natural five senses are pushed at the highest limits of human perfection; meaning that his sense of sight, touch, hearing, smell and taste are enhanced. With this ability he is capable of seeing further, acutely touching ink on a page, hear small sounds, have a smell capability similar to an animal and tasting accurately than normal members of their species.
- Enhanced Stamina: The serum, reduces the effects of fatigue allowing Roy to exert himself at peak capacity greater then any human Could.
- Enhanced Reflexes: Roy's natural reaction time is enhanced to a level beyond the human body's natural limits.
- Enhanced Speed: As with Jason it can be presumed that Roy's speed is greatly enhanced with the effects of the serum.
- Enhanced Longevity: With this ability he is at the peak of human conditioning. For this very reason, he age slower than normal members of his species due to having extremely healthy cells, without any superhuman degree. In addition, this power was activated when the he was in his young-adult years and he'd look twenty-years younger. Due, to this Roy should be able to live for at least 140 years.
- Rapid Cell Regeneration: The serum has greatly enhanced Roy's ability to heal. Within a day of getting stabbed by an arrow, Roy's scar was completely gone, and when glasses landed on his arm he was healed within a day.
- Flexible Bone Structure:Roy's bone structure allows him great flexibility. He can remain in a crouched position for a long time and perform contortionist type feats without causing any damage to his spine.
- Muscle Manipulation: Roy has complete control over the muscles of his, allowing him to freely alter and manipulate them, including altering muscle tissue itself, its development, increase/decrease muscle mass/strength and thus stamina, flexibility, reflexes, etc. He can move muscles without or keep them from moving, cause them to over or under-react to nerve-impulses, etc. He can cause/remove any muscle related ailments/diseases or cause muscles to react so violently he rip the tendons from their connections, snap bones or are themselves damaged
- Weapons proficiency: Roy can handle most type of firearms, having been trained in the army. He is proficient enough in handling small caliber to high caliber firearms such as a grenade launcher. He is also capable of handling Eva's bow, although not being as effective and efficient.
- Expert military operator: Roy is well-versed in intelligence gathering, decoding ciphers and other coded messages, infiltration, and espionage.
- Multilingualism: Based on what has been currently shown, Roy is capable of speaking English, Hindi, Japanese and Arabic fluently.
- Master marksman: Roy is a master marksman and highly skilled with many ranged weapons. This is partially supported by his proficiency with his eye scope. Roy's marksman skills are so great, he is said to never miss his mark, earning him the nickname Deadshot from Interpol.
- Aviation: Roy has skill in piloting advance aircrafts that include AXC Ships or the specially customized Panther Ship.
- Expert Swordsman: Roy is competent enough with his sword to take on three men carrying guns at close-range and emerge victorious.
- Computer Hacking: Roy is capable of hacking and some basic programming, but more importantly, of keeping his own computers and gadgets from being hacked or traced.
- Skin Hardening: Due to the effects of the serum, Roy can now harden his skin many times beyond the limits of human peak. He is capable of hardening his skin, increasing their defensive and/or offensive capabilities. This offers him not only greater strength but also greater durability and occasionally greater endurance.
- Cryokinesis: He can create, shape and manipulate ice, water frozen into a solid state and appears naturally in forms of snow, hail, icicles, ice spikes and candles, glaciers, pack ice, frost, and polar ice caps, and cold by reducing the kinetic energy of atoms and thus making things colder, for various effects and combinations. He can release/use ice/cold to attacks of various shapes and/or intensities, either projected, used as a part of melee attacks, etc. He can manipulate extremely cold energy capable of freezing anything it comes into contact with. This energy can be composed of an extremely cold gas such as air, or a magical energy. He is able to utilize ice manipulation with his physical combat, allowing him to both create tools and weapons for attack and manipulate the environment for their advantage (freezing the ground, sudden ice-walls, etc.). He can use ice to heal themselves or others, absorbing frozen energies and using them to freeze molecules, renewing damaged cells, causing him to stop bleeding. Ice can also provide energy to close up wounds, and allowing optimal health. He can generate and project ice from his entire body. He can produce pinpoint accurate beams of ice or sub-zero energy/gas that freezes everything it hits instantly. He is able to use a combination of cold, winds and snow to create blizzards of varying power to attack foes.