91's scheduled dep. @ WAS is exactly the same time as 92's sched. arr. It's impossible to arrive on 92 & leave on 91 the same day, unless 91 is running later than 92, which is not very common.
Of course, if you bought a RT ticket to RVR & were on time buy a RT to ALX from say RMT or PTB for example from RVR <> ALX. over phone. Reservation is on your phone and if necessary, get off before the meet with 91. Hopefully ALX or somewhere closer to RVR?