There have been 5 rovers sent to Mars:
Mars 2 Prop-M rover was launched by a Proton K Rocket and
carried by the orbiter.
Mars 3 Prop-M rover was launched by a Tyazheliy Sputnik Rocket
and carried by the orbiter.
Sojourner rover was launched by a Delta II rocket and carried by
the Pathfinder Orbiter
Spirit Rover was launched by a Delta II rocket and carried by
its orbiter.
Opportunity was launched by a Delta II rocket and carried by its
orbiter.