Striker Samuel arrived on an initial one-month loan deal from Reading on Thursday and goes straight into a U's squad which has lost its last seven successive matches and 10 of their previous 11.
But the U's have been dealt a couple of blows as they prepare to face a Rovers side just three points off top spot in League One.
Left-back Dan Potts has seen his loan spell cut short after he was recalled by parent club West Ham.
Defender Josh Thompson has also been told he is suspended for the clash at the Keepmoat Stadium following a mix up over paperwork.
Thompson was sent off on Boxing Day before turning his loan into a permanent move on January 1, however the deal was not rubber stamped in time for the New Year's Day defeat at Crawley and despite sitting out, his ban now applies to the fixture against Rovers.