so, you have a frame that fit 700c x 32. you might have 2 issues...
1. tire clearance. you already stated that tire clearance shouldn't be a problem, so we will drop that issue.
2. the other issue would be running a fatter tire on a narrow (roadie?) rim. a 32-35c tire will fit on a road rim with no problem. i run 32 and 35c on my cx, and I am going to try a 44c soon. i run both velocity aerohead and mavic open pros. i like the open pro's better in terms of durability (but i have a set of dt swiss r1.1 rims on the way to me soon!!!)
a fat tire/skin road rim combo can be troublesome... lots of pinch flats. sidewall and rim failure can occur and the ride will be VERY sloppy as slow speed.
you can correct the slow speed/sloppy feel problem by overinflating the tire, but then that would defeat the purpose of running a bigger/wider tire and would put alot of pressure/force on the rim.
so, i guess the question is....what rims do you have an what tire are you thinking of using???
with my aerohead....i think 35-38c is the widest i would ike to go. with the open pros and dt r1.1 rims....44c won't bother me one bit and i think there are some 29er guys running 2.1" tires on them!!!!
or, to answer you question....you can fit s 29erx2.1 on a road rim.....but if you did so, and actually rode on it....i think you would be asking for trouble.