A brand new SSD should not be partitioned.
Going by some other thread, You should be able to install RoonOS in UEFI mode onto a connected SSD. If this gives you an error, then maybe your SDD is corrupt/dying and needs to be replaced.
PS: You can also use an USB stick to boot into a more functional OS (Ubuntu desktop install media allows you to boot into Ubuntu Linux without installing) to inspect/format/partition your SSD.