And one of his alleged sex assault victims was warned by Peter Adamson, who played Len Fairclough in the soap, that he would "lead you astray", the jury heard.
The witness claims Roache indecently assaulted her when she was about 14 after he arranged passes for herself and her younger sister on a visit to Granada Studios in Manchester.
She told the jury at Preston Crown Court last week that Roache groped her in a room after being led past the Rovers Return pub on the set.
Today, she was cross-examined by the defendant's lawyer, Louise Blackwell QC, and claimed that Mr Adamson made the "cockroach" remark about the actor while she was at the studios.
"It was Len Fairclough that made the comment," she said.
"Because when he said it he looked directly at him and he looked at us and said 'You want to keep your eye on him, he will lead you astray' and he called him 'cockroach'.
"Len Fairclough said that he would lead us astray. He called him a cockroach with a capital C."
Roache, 81, of Wilmslow, Cheshire, denies two counts of rapes and five counts of indecent assault involving five complainants aged 16 and under on dates between 1965 and 1971.
The court heard that the alleged victim and her sister would sit on the steps outside the studio in the summer holidays in the mid to late 1960s, along with other girls and boys who were autograph-hunting.
But on one occasion after being invited inside the studios, Roache, who has played Ken Barlow in the ITV soap for more than 50 years, took her to his dressing room and indecently assaulted her by putting his hands on her breasts and up her skirt.
She told police: "He was like an octopus - hands everywhere."
Challenged about her account of what happened by Miss Blackwell, the witness told the court: "It happened, no matter what you are saying or what your job is, it happened.
"I have no reason to lie, no reason in the world."
Later Miss Blackwell put it to the witness: "Are you even trying to tell the truth here?"
"I'm telling the truth," she replied.
"Why the hell would I put myself through all of this?"
Roache was charged last May with two counts of rape on one alleged victim, with the publicity that following leading to the four other complainants coming forward.
The witness said she felt the incident had been her fault "for being there in the first place".
Her sister claims she was abused by Roache on a separate occasion.
The witness was asked by Miss Blackwell about press interest in her story and reporters visiting her house.
She said her sister had "two visits from the Mirror" and had been offered £25,000 for her story.
The witness added she was visited once by a reporter from The Sun, but the only money mentioned was a donation of an undisclosed amount to a charity.
"I know what's going through your mind," she told Miss Blackwell, "and it's not going to happen, because I did not want money."
She added: "If I wanted money I could've sold my story but I have not sold my story. I have spoken to nobody except those who should know."
As the cross-examination continued the witness agreed that she sometimes got details about times and dates wrong, but maintained she was telling the truth.
"I'm here as a witness," she added.
"I'm really hardly surprised that these people are not coming forward. If I had known what I was going to go through I would not have come forward.
"I feel as if I am on trial here. I have done nothing wrong here, it's Mr Barlow, Ken Barlow that's done it.
"I have done nothing apart from try to tell the truth. All right, I have got mixed up with a few dates, but the issue is what he did to me.
"I'm sorry but that's the way I feel - at the moment, as a victim, I'm so sorry I ever came forward."
The witness agreed that at first she told police the "cockroach" remark about William Roache had been made by the actor who plays the character Mike Baldwin, but said she later corrected herself when she realised it was Peter Adamson, who played Len Fairclough.
As the cross-examination closed, Miss Blackwell put it to the witness: "You have not been telling the truth at all."
"I have not come here to be called a liar and put myself through all these months of hell," the witness replied. "You can say what you want - I know it's true, he knows it's true.
"When I watched him on Coronation Street me and my sister were star struck.
"What we did not know, he had another name, that's Bill Roache, that was not a nice man. People (say), 'Oh yes, he's a lovely man on Coronation Street'.
"It's easy for you to stand there and judge, you were not in that room. I'm sorry, you was not in that room.
"He assaulted me, whether he likes it or not, and I have had to carry it around with me.
"Can you imagine what would have happened if I had gone as a child to the police?"