"I decided in the car," he said. "I have had a good innings and have decided it's the right time to quit."
Roche achieved two Classic victories in England when guiding the David O'Brien-trained Secreto to a 14-1 success in the 1984 Derby and partnering the 50-1 rank outsider Jet Ski Lady to win the 1991 Oaks for Jim Bolger.
The jockey was also on the mark with O'Brien's 1982 Irish and French Derby winner Assert, Bolger's St Jovite in the 1992 version of the Irish Classic and the Aidan O'Brien-trained Desert King in last year's running.
Other Irish Classic successes included Ballymore (1972), Nikoli (1980), the filly Triptych (1985) and Desert King (1997) in the Irish 2,000 Guineas.
And, in the fillies' version of the race, he was successful on board Sarah Siddons (1976), More So (1978) and Ridgewood Pearl (1995). He also captured the Irish St Leger in 1974 with Mistigri.
His weighing room colleague, John Reid, yesterday paid tribute to Roche: "I was in Ireland for three years for Vincent [O'Brien] and rode against him and the one thing about Christy is that he's a tough man in the saddle and a tough man out of it. He's not afraid of work - he's the hardest- working jockey and everything he has got, he has deserved.
"This game comes down to hard work and at the end of the day Christy was one of the hardest workers I have ever seen, and I think he will make a great trainer too, because he is not afraid of getting his hands dirty, and he is a hell of a good judge. His record speaks for itself. He has been a fantastic jockey over the years, very consistent right to the end. I rode in Ireland quite a bit and Christy never gave any quarter and hats off to him, he was a great rider."
Bionic was yesterday well backed to win next year's 1,000 Guineas with the bookmakers Coral, who were forced to trim her to 7-1 from 8-1 as the liabilities mounted up.
Only two fillies have so far attracted any support of note for the first 1999 fillies' Classic, the Henry Cecil-trained Bionic and Mick Channon's Bint Allayl, and they share favouritism in Coral's list.
"Bionic has been backed at all rates down from 33-1 and today's support took our liabilities on the filly to well over six figures," reported Simon Clare, Coral spokesman.
"Up until now the 1,000 Guineas ante-post market has lacked strength and depth and we desperately need some exciting performances by the fillies this autumn to explode it into life," added Clare.
1999 1,000 Guineas: Coral: 7-1 Bint Allayl, Bionic (from 8-1), 16-1 Etizaaz, 20-1 Valentine Girl, Fairy Queen, Crystal Charm, 25-1 Circle Of Gold, Kareymah, Pescara, Wannabe Grand, Mother Of Pearl, Mythical Girl.
William Hill: 7-1 Bint Allayl, Bionic, 16-1 Crystal Charm, 20-1 Etizaaz, Kareymah, 25-1 Circle Of Gold, Sakha, 33-1 bar.
Nap: Navarre Samson
NB: Ten Past Six