Which version did you try to install? 5.14? I had a similar problem on PowerEdge R210, but possibly from a different reason .. try to install version 5.11. That had been the highest version I could go.
Please let us know your results as it might confirm a suspected bug in ROS.
I installed the system on a Flash Memory (USB) and the place my DELL R610, boot and OS system: rip well but does not detect the disks but if you see the Dell SAS controller.
If I do the same with the HD system will not boot, stays in LOADING.
Attachment system images installed on USB flash memory in the Dell R610.
It seems like that ROS has no driver for your SAS controller. Maybe you can put in an additional SATA controller.
Just out of curiosity … can you upgrade the 5.11 to 5.14 on your USB stick? 5.12-5.14 doesn’t run at all on my Dell that is similar to yours. I have not been able to determine if that is due to the CPU or something else.
Another thing you can do is to install KVM / Xen / Virtualbox on your server and emulate a more standard hardware and install ROS inside that. There is a little performace hit (3-5%) … but your HW seems to be strong enough.
Could you boot 5.14 from the USB like you did with 5.11 . I know that it may not help your problem, but it could help me verify my problem with the dell server.