Imorrison,
Let me guess, you're talking about the Rattlesnake Wilderness and the corridor out of Missoula. If thats the case, you need to specify as there are different firearm regulations there.
Your first post didnt mention anything specific about the area you were in...only asking if you had to be 150 yards off any road on any FS land to shoot a deer. The fact is, behind gated roads, you can stand in the middle of the road and blaze your way into glory. You arent breaking any law. In almost all the rest of the State, you only have to be off the normal right-of-way to fire a weapon, including highways, county roads, etc.
Its all in the regulations...and I could find it 1 minute on the MTFWP website or with a 2 minute phone call to the FWP.
I'm also assuming you likely strolled into the MTFWP office and chatted it up with the front desk help. If you have specific regulation questions...Dan Curtin is your source, and I dont care if its info about the Rattlesnake corridor regs, or any other state regs...he knows. Biology related stuff...Mike Thompson, Jamie Jonkel, Jay Kolb are your guys for the Missoula area.