R7515 support BOSS S1 controller and BOSS S1 supports SATA SSD. Below link have details on drives supported by BOSS S1 [URL] You can use below part# for latest BOSS S1 based on your slot type.  
I'm looking for a BOSS controller adapter that supports M.2 NVME drives for my new Poweredge R7515? It seems like it still comes with the BOSS-S1 version instead of the newer S2 version, but I'm having a hard time figuring out which model number goes with the R7515 (or do all of the S1's work?) The 72WKY seems to be the most common when looking for the low-profile version but it's hard to know for sure. Does anyone know the right model number I should be searching for?
Dell PowerEdge R7515 and M.2 NVMe?