"I already knew Mike McCarthy from school and with Wasps and he was influential in my signing.
"He told me about the set-up here and about Michael Bradley's style of coaching and it sounded like something I'd be very interested in becoming a part of."
Roberts, who won three Premiership titles in England with London Wasps as well as a Heineken Cup medal, has already settled into training in Galway.
"Since arriving, training has gone really well. There is a great atmosphere in the dressing room and we're all looking forward to hitting the ground running come the start of the season," he added.
CEO Gerry Kelly said Connacht were impressed with Roberts' prolific scoring record with his previous clubs, and he is just the calibre of player they have been looking for.
"He is a very strong running, powerful winger and his record is a testament to that," Kelly explained.
"He was the top try scorer for Glasgow in his first season there and scored a few hat-tricks in his time with Wasps so we're looking forward to him bringing that kind of form to the Sportsground."