> Trains to Roi Et are quite available.

Sorry, no train line to Roi-Et. The nearest lines are at Buriram or Khon Kaen.

There are two airlines flying to Roi-Et however, Nok-Air and Happy-Air.

Happy-Air flies from Suvarnabhumi, while Nok-Air flies from Don Muang
(or at least they did a few months ago)

Happy-Air is a bit cheaper than Nok-Air, but both are excellent.