But when he first stepped foot in Weatherfield in 1960, he never dreamed he would still be appearing in major storylines when the ITV soap celebrated its 60th anniversary.
Like many jobbing actors he feared he would be axed – and this fear was heightened by the fact Ken did not really seem like a natural resident of the Street.
He says: “The trouble with Ken was he was an educated university graduate from a little back street. So why is he still there? He would have moved on. He would have gone up in the world.
“There had to be that element of failure. It was mainly in his relationships.
“Of course, he always wanted to write ‘the book’ and that never happened. So you had to have all that. It was a tricky one to overcome.”
But Roache has found Ken a welcome long-term companion.
He says: “Ken has always protested for what is right. He took part in the CND marches and anti-Vietnam War protests in the sixties.
“He always takes a stand for peace, love and a caring community. I am very much in tune with that.”
Roache thought his time was up as long ago as in 1971 when Ken’s first wife Valerie was killed off in 1971 – electrocuted by a faulty hair dryer.
Last Tango in Halifax star Anne Reid, who played Valerie, had wanted to go but Roache feared the bosses might make him leave too.
He says: “I wondered then whether they were going to keep me on or not. I didn’t know. But that was very early on.”
At other points, he briefly considered quitting. “In my forties I had a long think about it and really looked at the whole thing,” he says. “But I just loved it so much. I thought about leaving but not really seriously and I never put it into action in any way whatsoever.”
Now Roache, 88, is the sole remaining member of the original cast, is still firmly ensconced at 1, Coronation Street – and holds the Guinness World Record as the longest-serving soap star,
He has appeared in more than 10,000 episodes during which there have been 57 births, 146 deaths and 131 weddings. The loss of Valerie was only one of a long list of tragedies Ken has had to endure.
His second wife died too, as did his parents and his younger brother David.
Roache says: “Ken was a bit of a one-man Greek tragedy.”
For the milestone anniversary on December 9, he is involved in not one but two huge storylines. In one he is pitched against the villainous Ray Crosby in a battle to save the very bricks and mortar of Coronation Street.
Roache says he loves the plot, in which he and the other residents stage a sit-in protest to stop the developer’s demolition plans.
He says: “He feeds off being hated. It’s almost like he loathes the sentimentality of Coronation Street and hates that idea of community.”
Ken, of course, is the polar opposite of this. His other big storyline involves troubled son Peter falling off the wagon – and discovering who Carla has been sleeping with.
Roache says: “He cares about his family, even though they really are dysfunctional. That’s wonderful and long may that continue.”
But right at the start, 60 years ago, Roache at first turned down the role because he wanted to make his name in London.
He finally accepted it when his agent told him it would only last for 11 weeks.
Now, 60 years on, ITV soap boss John Whiston has praised his staying power, saying: “What an amazing career. Bill is a real marathon runner. It’s incredible.”
Roache reckons the show, which still tops the ratings with a regular audience of seven million, will continue to run and run. Praising loyal viewers, he says: “We’ve become lifelong friends. And for that loyalty I’m eternally grateful.”
He is looking forward to celebrating Ken’s 100th birthday with a pint in the Rovers. He adds: “I’m some eight years older than Ken so I will get there first.”
Three one-hour Coronation Street specials will air on Monday 7, Wednesday 9 and Friday 11 December on ITV at 7.30pm.