Kryklia holds notable wins over: Iraj Azizpour (2X), Guto Inocente, Murat Aygun, Andrei Stoica, Tarik Khbabez, Rade Opačić, Nordine Mahieddine, Fabio Kwasi, Jahfarr Wilnis, and Sergej Maslobojev.

With the club "Burovik", Kryklia began to fight at the Ukrainian Kenpokai Karate and Kickboxing championships, among children and youth, and won a number of medals.

He then took part in the 2015 Tatneft Cup heavyweight tournament, scoring knockouts of Claudiu Istrate in the semifinals and Daniel Lentie in the finals.

In June 2016, he won the A1 WGP qualification tournament by knocking out Thomas Vanneste in the semifinals, and by forcing Daniel Lentie to withdraw at the end of the first round in the final.

Kryklia won the quarterfinals against Bosnian Bahrudin Mahmić, semifinals against Atha Kasapis and finals against Fabio Kwasi in the same manner - knocking all three with a knee strike.

[18] In the semifinals of the 2018 FEA World Grand Prix, Kryklia was scheduled to fight a rubber match with Tomáš Hron, with each fighter holding a win over the other.

He defeated Martin Pacas by unanimous decision in the quarterfinal, and Rade Opacic by a second round TKO in the semifinal, before fighting a rematch with Iraj Azizpour in the finals.

[20] On November 16, 2019, Roman Kryklia defeated Tarik Khbabez by TKO to become the inaugural ONE Light Heavyweight Kickboxing World Champion.

[21] Kryklia was expected to defend his belt against Andrei Stoica at ONE Infinity 1, but the light heavyweight title fight postponed due to coronavirus.

[28][29] Kryklia was scheduled to make his second ONE Kickboxing Light Heavyweight title defense against Murat Aygün at ONE Championship: NextGen on October 29, 2021.

[30] However, Aygün was pulled from the fight and Kryklia was instead scheduled to face Iraj Azizpour for the inaugural ONE Kickboxing Heavyweight World Championship.

[36] Kryklia was booked to face Iraj Azizpour in a trilogy bout in the finals of the ONE Heavyweight Kickboxing World Grand Prix Tournament at ONE 163 on November 18, 2022.

[38] Kryklia was expected to make his third ONE Light Heavyweight Kickboxing World Championship defense against Françesko Xhaja at ONE Fight Night 12 on July 14, 2023.

[40] Kryklia faced Alex Roberts for the inaugural ONE Heavyweight Muay Thai World Championship at ONE Fight Night 17 on December 9, 2023.