Rovers progressed on Tuesday night thanks to goals Matty Taylor and Jermaine Easter against Wycombe Wanderers and whereas Southend won 0-3 away at Crawley Town.
Darrell Clarke's men were ball number 1 in the draw that took place live on Soccer AM.
The game will take place on the week commencing 9th November at Roots Hall.
Full Southern Draw:
Daggenham & Redbridge vs Oxford United
Gillingham vs Yeovil Town
Southend United vs Bristol Rovers
Plymouth Argyle vs Milwall