If you are going to try and convert D&D adventures, then bear in mind that the dynamics of combat make a major difference, particularly at higher levels.
Where D&D parties can easily cleave their way through low level hordes, RM players will find that any battle that leaves them heavily outnumbered a major struggle.
Also, creatures such as dragons and the bigger giants are much more powerful due to the Super Large critical tables.
Finally, remember to warn your players that RM combat is MUCH more likely to get them killed, and so it is often better to avoid combat.
Bear these in mind and the 1.5x rule works pretty well.