Jason Floyd of MMA Report broke the news.
The bout, which will take place on the UFC 166 preliminary card, is slated to go down later this fall (October 19, 2013) at the Toyota Center in Houston, Texas.
Roop (14-9-1) looked like he might be on his way out but has reignited his career since dropping down to the bantamweight division for the second time, which gives him a tremendous size advantage over his opponents due to his 6'1 height. He most recently shocked the MMA landscape by putting away former WEC champion Brian Bowles at UFC 160 in June.
Rivera (9-2, 1 NC) has looked re-energized in his second stint with the promotion. He crushed Edwin Figueroa at UFC 156 via second round knockout and also blasted the durable Roland Delorme at UFC 149, although that victory was overturned after a positive test for a banned substance.
A victory could set up either man for a top 10 position in the UFC's growing bantamweight division.
UFC 166 features a heavyweight title fight trilogy with Cain Velasquez vs. Junior dos Santos 3, a co-main event between Daniel Cormier vs. Roy Nelson, and an intriguing welterweight bout featuring former Bellator and Strikeforce champions Hector Lombard vs. Nate Marquardt. For the latest UFC 166 rumors and event updates, click here.