will they work together or do i need to use my sram bb?
Related question for the gear heads. Will an FSA bottom bracket work with Ultegra Crankset?
No, the non-drive side is different than the drive side on a SRAM BB. There is a step in the non-drive side of the GXP that deals with bearing load and the inner diameters of the drive side and non-drive side are different. You need that. So SRAM GXP cranksets were never meant to be usable with a Shimano BB and vice versa.
You may also run into problems using an Ultegra crankset on an FSA bottom bracket. They are supposedly compatible, but I’ve found that the spindle sizes are not exact. Whenever I’ve put a Shimano crank into an FSA BB - which I’ve done a couple times since I helped some friend’s mount SRMs on their Soloists - there has been quite a bit of slop. It seems that Shimano either does a tighter job on variance, or there is just a slight difference in OD between the two. FSA also appears to run a narrower outer bearing, which may also affect your ability to really get your crankset snug. Regardless of the fact that many of these things are supposed to be cross compatible, they don’t actually seem to be in practice. It’s like a standard that isn’t really standard…
As was mentioned, NO. They can be made to work with shims/washers, but the non-drive side is narrowed (from 14 to 12mm I think) and you won’t be able to get the crank arm on tight. Will need SRAM Red Giga Pipe (or whatever it’s called) if you want a ceramic BB.
Related question for the gear heads. Will an FSA bottom bracket work with Ultegra Crankset?
The BB-8200 Ceramic bottom bracket (red bearing cups) should work whereas the non-ceramic BB-8000 bottom bracket is probably not going to give the correct spindle spacing as the FSA cermic bottom bracket uses narrower bearing cups and may even require the use of the FSA wave spring washer to eliminate lateral play. I doubt this will be the case based on experience with FSA Energy Cranks in which the crank arm attaches using a similar design to the Shimano Dura Ace/Ultegra cranks and when I have installed those cranks on my cross bike, no spacer was required with the BB-8200 ceramic bottom bracket.
another option is Superfly Cycles in Boulder. I have one for my SRAM red crank and have been very happy with it so far.
http://www.superflycycles.com/servlet/-strse-272/Enduro-Ceramic-Road-Bottom/Detail