Monakana started his career at Arsenal and scored six goals in 49 appearances at Preston before joining Brighton in January 2014.
But Monakana has yet to make a first-team appearance for the Seagulls and has spent time on loan at Crawley, Aberdeen, Mansfield and Carlisle.
Rovers manager Darrell Clarke told the club’s official website: “Although he’s only 21 Jeffrey ticks a lot of boxes; I watched him play a couple of years ago and he caught my eye then.
“For a 21-year-old he has a lot of appearances under his belt and he was keen to come here to further his experience.
“If he does well hopefully we might be able to extend his loan, but for now I’m delighted to have another option for the right side of midfield.
“I think he is a key piece in the jigsaw as he is a natural right winger and in Cristian Montano we have a natural left winger.”