The Galway born player began his career with League of Ireland First Division team Mervue United before joining Premier League team Limerick in July 2011.
He signed for Cambridge in January of this year, though didn’t make his debut for them until September.
His six appearances for The U’s to date include two goals, on his first start for the club, against Yeovil Town.
Of his new signing, manager Darrell Clarke said; “He is a lad I have heard about, through my contacts, from his time in Ireland and who gives us a different option in attack and I am looking forward to seeing how he does with us for a month.
“Rory came on as a substitute for Cambridge when we played at The Abbey Stadium recently and will be joining us, initially, until 2nd January.”
Chairman Nick Higgs added; “We will continue to back Darrell as he adds to his squad. Rory is the second player to join us on loan this week and I wish him every success during his loan spell.”