Rovers have agreed a one-year deal with former Manchester City striker Benjani, with an option for a further year.
The paperwork wasn't completed in time for the Zimbabwe international to be considered for tomorrow's game against Arsenal.
An exclusive interview with Benjani will be available to Rovers Player subscribers on Saturday morning.
A Zimbabwe international captain with over 40 appearances on the world stage, Benjani started his professional career at South African club Jomo Cosmos before his goalscoring exploits caught the eye of European clubs.
After an initial loan spell at Grasshoppers Zurich, Benjani signed for French side Auxerre, enjoying a four-year spell.
A move to Portsmouth followed in 2006 where he scored 19 goals from his 70 appearances before signing for Manchester City in 2008.
Injuries limited the striker to just 23 appearances during his time at City, scoring 4 goals, his spell at Eastlands ended when he finished last season on loan at Sunderland.
