Molerats no idea
The Dust scorpions work for small Rad scorpions, they are about a little less than an inch long.
Mirelurks , nothing I have seen.
Dogs Undead hounds, guard dogs depending on how picky you are, for me any dog that looks vicious or starved works.
Rad roaches the closest from reaper is their beetles of diffrent kinds, but I have not found any good roach models from any manufacturer, the closest are plastic toys.
Brahmin, nothing from reaper, the best ones are from armorcast or made from 1:48 plastic cows.
Bloat flies once again, nothing for reaper,unless you want a huge one, then the Fly demon might work. Armorcast does a set of three ok ones.
Sorry I could not be more helpful, perhaps someone else has better sugestions.