The rotaries are considered MOW equipment, not locomotives, and so do not fall under 49CFR230. The trucks, etc., would be inspected like any other piece of MOW equipment, and the boilers are inspected by the State. (Ditto a steam crane or pile driver if one existed.)
I seem to recall that OM and OY's boilers are certified by the Colorado boiler inspector. I'm not sure why, and that memory may be faulty.
JAC