Striker Campbell has moved to Ewood Park on a 93-day emergency loan from QPR while free agent Williamson penned a permanent contract until 2014 on Friday.
Should Campbell make his Rovers bow, he would face the team where he spent the latter part of 2012 on loan at. The 31-year-old struck 10 times in 17 appearances for the Tractor Boys.
Rovers will assess the fitness of centre-back Grant Hanley after he returned from international duty with Scotland this week ahead of the 1-0 win of Estonia due to a hip complaint.
Elsewhere, boss Michael Appleton has no other new injury problems.
Former Manchester United forward Josh King remains out alongside Adam Henley (both hamstring) while long-term victim Leon Best and midfielder Dickson Etuhu are sidelined due to knee injuries.
Bradley Orr returned to start at right-back in last weekend's 2-0 home win over Bristol Rovers following a loan spell with Ipswich and is set to retain his place against the Tractor Boys.