The pair had no speaking time before entering the CBB house last week.
We can reveal they had a series of spats while they shined 10 years ago in rival soap operas.
Roxanne played Jo Sugden in Emmerdale, while Ryan Jason Grimshaw was in Corrie.
Their confrontation came hours before they appeared on the red carpet at the British Soap Awards.
"In a conversation she asked Ryan," why do you get involved? "Ryan told her then that she did not have to speak to him, and things did not improve after that."
Ryan learned that Roxanne would wear the same dress as one of his co-stars.
He called her and demanded that she change her outfit at the last minute.
A TV insider said, "Ryan felt like he was doing the right thing by trying to match his friend, but Roxanne was surprised by the way he dealt with it." He did not like his tone and refused to do so. what he had asked for. "
A few months later they clashed again in a row about her then-relationship with Richard Fleeshman.
Ryan had seen Roxanne chatting with a male friend and assumed she was flirting
Our source said: "Ryan warned Richard that he thought Roxanne was not good enough, which was not true. "Roxanne was furious that she had been painted away as something she was not."
"In a conversation she asked Ryan:" why do not you you you? & # 39; Ryan then told her that she did not have to speak to him. Things did not improve after that. "
Roxanne, 35 and Ryan, 34, have not been in a good condition since their rows.
The long-term feud will certainly make their stint awkward in CBB.
Showbazen hope that their time together will reopen old wounds and they will have it on camera.
An insider said, "It always works well for CBB when a rivalry of the real world comes to a climax in the show.
"In 2014, viewers were gripped by the hostility between Jim Davidson and Linda Nolan, and Bosses would like something like that to happen again."
Ryan has so far been popular with viewers. During a vote at the live launch show of Thursday, he was chosen to be vice president.
A TV source said: "It is well known in soap rings that Ryan likes to become a top dog, and we are almost certain to see that side of his personality while he is in CBB."
"When he throws his weight around it, it is likely that Roxanne will not stand it. "
Roxanne and Ryan have both come out early as favorites to win the series.
Bookies William Hill offer odds of 5/2 that Ryan is crowned champion in the final of next month Roxanne is second favorite on 5/1.