They are a welcome addition, with the province's England-capped prop Robbie Morris sidelined due to a back injury.
South African Rogers, 26, played with the University of Cape Town before being called up to the Griqualand West side in the Vodacom Cup this season.
The promising Ah You, who has been capped by New Zealand at Under-19 and Under-20 level, joins the westerners from NPC outfit Canterbury.
He won IRB Junior World Championship titles with the Baby Blacks in 2007 and 2008, and has signed an 18-month deal with Connacht.
Elwood said: "We're delighted to have the two guys on board. They offer us options to mix our team up a bit.
"The inclusion of the Italian teams in this season's Magners League means four extra games and with the Amlin Challenge Cup as well, it is important to be able to give guys a rest and rotate the squad.
"We are also very happy to be able to give these young promising rugby players a chance to prove their worth on the big stage.
"Connacht have always offered opportunities for players to hold their hand up and rise to the challenge. These guys are big mobile forwards and we feel they will fit into our set-up very well."