[2] Soldić made his MMA debut 19 September 2014 at AFC 3: Arti Fighting Championship 3 in Ljubuški, Bosnia and Herzegovina in the lightweight division against Ante Alilović.

In the same year, he scored another win when he defeated Mladen Ponjević via submission (guillotine choke) in the first round (00:35) at a MMA event in Metković, Croatia.

[7] Roberto Soldić scored his first major win and attracted local media attention at Serbian Battle Championship: SBC 5 in May 2015 in Odžaci, Serbia, where he fought Vladimir Prodanović.

He won the title at SBC 8 that took place 5 March 2016 in Sombor, Serbia, when he defeated experienced Montenegrin fighter Vaso Bakočević via TKO in the third round.

After two rounds, judges decided in favor of Radaković which caused upset in regional MMA circles and media which claimed that Soldić scored more points.

In a welterweight title bout that also served as the main event, Soldić defeated Pascal Kloser via TKO in the first round (1:34).

Soldić and his team decided to take a shot at the Final Fight Championship title against one of the most experienced Croatian MMA veterans Ivica Trušček at FFC 27 – Night of Champions that took place 17 December 2016 in Zagreb, Croatia.

[16] After a high kick that stunned Trušček, Soldić began a ground-and-pound leading to referee Grant Waterman stopping the match.

Roberto Soldić thus became the FFC welterweight champion in a match prior to which he was considered the underdog in comparison to his more popular and experienced opponent.

[23][24] On 14 October 2017, Roberto Soldić made his Cage Warriors Fighting Championship debut at CWFC 87 when he locked horns with Lewis Long.

[27][28][29] In December 2017, two months after his win in the match against Lewis Long, Roberto Soldić stepped into the cage for the fifth time in one year in Polish MMA promotion Konfrontacja Sztuk Walki (KSW).

By stepping up on ten days’ notice and accepting a welterweight title bout, Soldić decided to take the biggest test in his professional career.

Mankowski's original opponent Dricus du Plessis was forced to withdraw from the match quoting an injury.

[37] The two would later rematch at KSW 45: De Fries vs. Bedorf, with Soldić defeating du Plessis via third-round knockout.