The 28-year-old joined The Pirates after mutually agreeing to end his contract with The O's after falling out of favour with the East London outfit.
Thorpe, who recently spent time on loan with Grimsby Town, put pen-to-paper on a two-year contract with the struggling West Country club and Thorpe is looking forward to his new career at The Memorial Stadium.
"There was interest from elsewhere, but I'm pleased to be here and I'm looking forward to it," Thorpe told the club's official website.
"The length of the contract Rovers have given me helps, and as a player, you always want to play for a big club which is what I feel Bristol Rovers is.
"It was a hard decision for me at first because I've moved around a lot, and living-wise I wasn't sure if I wanted to come to this side of the country.
"But now I've come over and seen the club and spoken to the chairman (Geoff Dunford) I think it's great here and I'm really pleased to be a Bristol Rovers player."
Meanwhile, winger Wayne Carlisle looks to be out for the rest of the season after being told he needs surgery on his injured knee.
In other news, the club may be close to making a managerial appointment after caretaker boss Phil Bater revealed on Saturday that he was considering his future with Rovers following a 4-0 away thrashing at West Country rivals Yeovil Town.
