I am not familiar with ROIcoin but having looked at the git page it appears that it is memory focused and not cache focused. Please correct me if I am wrong.
https://github.com/ROIcoin/ROIcoin

As for HP DL580 G7 memory and memory configuration here is a link:

HPE ProLiant DL580 G7 Server - Configuring Memory
https://support.hpe.com/hpsc/doc/public/display?docId=c02283239

Look at the "Memory performance optimization" section in the above for suggestions to obtain the best memory speed.

And if you are using eight memory cartridges be sure to turn on Hemisphere mode.

Also be sure that NUMA is enabled in the BIOS (ACPI SRAT) :

HPE ProLiant DL580 G7 Server - Configuring NUMA Memory
https://support.hpe.com/hpsc/doc/public/display?docId=emr_na-c02142071

I want to point out that you may be able to run with a single cartridge installed in slot 1. If you are using 8GB memory modules you can put 64GB in a single module. When this is done all the processors can access the memory in that single cartridge. Processor 1 has a direct link and processors 2, 3 and 4 has to do a hop through processor 1 to get to it. I am running all my HP DL580 G7 systems with a single cartridge and it only slows down monero mining by 1-2%. Monero mining is cache bound and not memory bound. The slowdown may be different for mining ROIcoin.

I suggest testing with these configurations:

Only one cartridge in slot 1

Four cartridges in slots 1, 3, 5, 7

All eight cartridges

Getting back to mining ROIcoin I have tried to find out how it actually works when mining. I have tried searching but have been unable to find an example of the config file. If you could post an actual config it would be helpful.

Here are my assumptions:

Since ROIcoin mining uses a 1GB AES Pattern Search PoW (HOdl) in memory I assume that each processor CORE is working on a single instance of this 1GB of memory.

If that is how it works then each of the eight core E7-8837's need access to 8GB of memory or 64GB total memory. Which can be in 1, 4 or 8 cartridges.