But they will be without striker Ellis Harrison for the second leg next week after the 21-year-old was sent off late on for a second bookable offence.
His needless clash with Steve Arnold, after the Forest Green ‘keeper collected a routine save, scraped the shine off a promising night for the Gas, whose early goal through Matty Taylor proved to be the winner.
Rovers dominated the opening half, with shots from Chris Lines and Taylor going close before the latter latched on to a long diagonal ball, rounded Arnold and slotted home from a tight angle on 17 minutes.
The visitors to the Cotswolds also hit the post through Harrison’s header before half-time and Taylor had another goal ruled out for offside in the second half after Harrison headed a cross towards goal.
Forest Green piled on the pressure at the death and captain Charlie Clough saw his back-post header bounce back off the crossbar deep into stoppage time.