He was hired by Thawn to sell guns to the Swampies on Delta III. This would allow Thawn to justify killing the Swampies as they posed a threat.
The Swampies tried to used the guns and they misfired. Realising they had been tricked they took Rohm-Dutt prisoner. He was tied to a rack alongside the Fourth Doctor and Romana I. They were tied with vines that would tighten in the sun until their backs were broken. They escaped and were pursued. Rohm-Dutt tripped and was dragged away and killed by Kroll. (TV: The Power of Kroll)