The news comes as a blow to coach Clive Griffiths, who is also missing his stalwart loose forward Jono Smith.
It is not known how long Roets will be out for.
Griffiths said: “We don’t know yet how long he’ll be out, but it’s a big blow.
“Leon Brennan is doubtful for Sunday with a shoulder injury and Danny Hulme and Kris Wilkes will be assessed at training on Thursday.
“That’s five players we’re struggling with, and they’re five players who are huge for us.”
Crusaders take on Whitehaven on Sunday, and Griffiths knows the game will be tough for the struggling Welsh outfit. However Crusaders are going into the game on the back of a 36-32 win at Oldham last week.
He said: “We’ve had a few confidence boosters already this year, but we haven’t kicked on. We’ve got a very dangerous opponent in Whitehaven, and the challenge for us is to back it up.
“Getting back-to-back wins would be fantastic. We’re a new team and everyone’s got high expectations, but we’re rubbing shoulders with some teams that have been established for more than 100 years.
“Rome wasn’t built in a day and neither will Crusaders be. We’ll take the good times and battle through the bad times, but there’s a great determination to carry this through and become an established team.”