I've been getting several reports of crashes when people take tModLoader and apply RomTerraria on top of it.
While the latest version of RomTerraria includes updates to handle the base cases, I'm still trying to figure out the cause of a race condition with rendering that appears to be affected by certain mods.
If you are experiencing crashes with a modded Terraria with RomTerraria applied, please reply to this post with the list of mods that you are adding.
Update 3/26/2017 4:23pm: Fix coming shortly.
Update 4/3/2017 7:04pm: I'm still working on a global fix. The major cause of most of these problems (and crashes with non-retro lighting) appears to be assumptions about the state of the SpriteBatch object. If a mod works in retro mode, but not in other lighting modes, it's a bug in the mod. I'm working on a deeper fix, but it's going to take a bit more time.