The 23-year-old attacker, who began his career at West Ham, was sacked by Oldham in 2013 after being arrested for spot-fixing, though no charges were ever brought against him.
The Colombian has been playing in his home country and joins up with Rovers as they begin life back in the Football League, subject to international clearance.
Manager Darrell Clarke told the club website: “Cristian can play wide right or left and he has impressed me every time I have seen him play.
“It’s fair to say that he comes with quite a lot of baggage and I have spoken at length with Cristian and his advisers before deciding to offer him a contract.
“I know that he is desperate for another opportunity to play League football and I’m a firm believer in giving everyone a second chance.
“I have also spoken to two of his former managers, who have given him glowing references, and he is a player who will excite our supporters, I’m sure.”
Chairman Nick Higgs added: “I agree with Darrell in that everyone deserves a second chance and I would like to welcome Cristian to Bristol Rovers and hope that he enjoys a successful career with us.
“He has an excellent footballing background and I think he will be a huge asset to the club. Signing players who could give us some width was always going to be a priority and we hope to make further additions to the squad in the coming weeks.”