Step 1: Get roster (obviously). Save it to desktop.
Step 2: Download
http://www.game-tuts.com/community/modio.php
Step 3. After extracting modio to desktop open the exe.
Step 4. Go into Xport 360. (you must have a Backbreaker save; load up backbreaker once and you should be fine)
sub-step 1. Load and click your 360.
sub-step 2. Click Partition 3.
sub-step 3. Click Content.
sub-step 4. Click E00000C9D8264E12 (should be the second option).
sub-step 5. Scroll down to the bottom and find the file that says Profile Options (464F07DA). Click it.
sub-step 6. Click the 0000001 thing.
(keep this open)
Step 5. Go to the roster you want to put into backbreaker and move it to desktop for ease of access.
Also, rename it. Add a b to the end of it's name (BBCUST14
b).
Step 6. On your X-port screen take BBCUST14 and move it to the desktop by your roster file (which should be BBCUST14b if you listened to me).
Step 7. Now back to the Modio thing. Drag first BBCUST14 into it and situate it so that you know where it is (the left hand part of the screen would be good). Then drag BBCUST14b into modio (put it opposite of BBCUST14; the right would be good).
Step 8. Locate BBCUST14 in modio (should be on the left if you listened). Copy the profile ID number and paste it into BBCUST14b's Profile ID. Do the same for Device ID (from BBCUST14 to BBCUST14b). Close BBCUST14 (not b).
Step 9 (the easy one). Click Rehash and Resign on BBCUST14b's file thing.
Step 10. Close modio. Delete BBCUST14 from your desktop. Rename BBCUST14b so that it no longer has a b and is BBCUST14 again.
Step 11. In Xport, delete the BBCUST14 that is there and move the BBCUST14 from your desktop into the file.
You should be good to go. Have fun.