The 30-year-old Senegal international has been without a club since he was released by Blackburn at the end of last season. A two-time African Footballer of the Year, Diouf was a £10million arrival at Anfield in 2002 after playing a starring role in Senegal's successful World Cup campaign that summer.
Often a controversial figure during his time in British football, Diouf has also played for Sunderland in the Barclays Premier League and helped Rangers to the Clydesdale Bank Premier League title during a loan spell north of the border last term.
Diouf's arrival at the Keepmoat Stadium will go some way to addressing the striker crisis currently engulfing Rovers boss Dean Saunders.
Goalscorer James Hayter was the only established centre-forward in the squad for the 1-1 draw with Coventry on Saturday as Billy Clark missed out due to family issues. Fellow striker Chris Brown has only recently resumed light training following a knee injury and Jon Parkin returned to Cardiff at the end of his loan period in Yorkshire.