First, your base track/pivot needs to be installed on a FINISHED surface (other than carpeting.) If you're installing the base tracking in a carpeted room, usually, you 'cut' the carpet where the track is laid, and re-tack the carpet in the closet and in the 'main room' right up against the track. This way, it looks like the carpet was installed AFTER the track/pivot. Now, some installers will go over the carpeting. THat's OK if you can live with 'the look' ...
As far as the rough-out measurements, you need to measure the THICKNESS of the top track and the thickness of the bottom track, and add 3/4". YOu can 'shim' the bottom if you need to, or cut the bottom too. Of course, you REALLY don't want to do either so you have 2 options: 1) Assemble the door on the floor, top and bottom, and measure up. Check that the 'adjustable' parts are NOT 'unscrewed' all the way! Set them at a half-setting. THen measure. Add that number to the thickness of the drywall above the doorway, and that total is the HEIGHT of your rough opening. Do the same for the sides, adding 3/4" to the WIDTH of the doors, plus (the thickness of the drywall x 2.) That's your rough opening.
This 'stuff' is EASIEST to determine if you can find the Installation Instructions that come w/the doors. My best to ya and hope this helps.
PS: Sometimes, the BOTTOM track is only 1/2" in thickness. This is NOT enough for carpeting! YOu want a track that's at least 3/4" up to 1" in height for the bottom. If you can't find a track this thick, contact Stanley Hardware or any True Value store to order some. (THey have bi-folds too.) If you have pivot doors, there's no problem; you can 'shim' the pivot. (I don't use pivot bi-fold doors.)