The 30-year-old has been bedevilled with various injury problems since signing for the Light Blues from Anderlecht in 2020.
Roofe stayed on the bench for the 4-0 cinch Premiership win over Hibernian at the weekend and missed the goalless Europa League draw against Sparta Prague on Thursday night, and will not be in the squad for the visit of Hearts on Sunday.
Clement did not reveal the specifics of the former Leeds forward’s problem, although he was reportedly sent for a scan on a groin complaint in September under previous manager Michael Beale.
“Kemar will not be available for the weekend for sure,” said the Belgian boss. “Probably we need to rebuild.
“In the next weeks, we need to take a really good look at that because he has been struggling for a long time with the same things.
“It is important to find the reason for that and not always find the solution to get him fit for the next game and struggling afterwards again and going game by game, but really going to the cause of the problem.
“I cannot say anything about that (how long he will be out), we first need to make a really good assessment of how to bring Kemar back in a way that he can be a long time back and not a short time because that has been the case the last couple of months, to get him fit for games but struggling in between so we need to get him really fit.”
Clement was speaking on a Zoom call following what could be a vital Europa League point in the Czech Republic.
Striker Danilo, on his way back to full fitness following a facial injury which requires him to wear a mask on the field, came off the bench and was closest to scoring for the Ibrox side when his shot was tipped on to the crossbar and over by Sparta goalkeeper Peter Vindahl.
Clement believes it will still be several weeks before the Brazilian forward is back to his best.
He said: “He has (been) out for quite a while. He didn’t play so many 90 minutes in the last couple of months or even the last year.
“He looked bright in the short period he played, but it is about making him stronger so that he can reach that level for 90 minutes.
“It is a work of several weeks to bring him to that level.”
Borna Barisic missed the trip to Prague with a knock and Clement is not sure if he will have the left-back available for the game against the Jambos.
He said: “We will see if Borna can train tomorrow, that is still a question mark.”
Clement hopes midfielder Jose Cifuentes will resume training on Saturday, but Tom Lawrence, Rabbi Matondo and Dujon Sterling remain out.