Roon is rather like Lego - there’s a few basic components that can be put together in many different ways. It sounds as though you have an “all-in-one” Roon software package installed on your Dell at the moment. If that meets your needs, and you’re happy, there’s no need to move.
Some people (including me) prefer to have the Roon Core component installed as a music server that runs 24/7, which feeds a variety of audio endpoints, and which can be controlled via the Roon user interface running on a variety of devices (tablets, PCs, smartphones); just grabbing the one nearest to hand to access and set up the music that we want to hear and where we want to hear it.
That Roon Core component (the Roon Server) can be installed on a PC or Mac or a NAS.
ROCK is a packaged Roon Core together with a minimal operating system that can be installed on an Intel NUC kit to make what is, in effect, a Roon Server appliance - it’s not a general-purpose computer like a PC or Mac.
Personally, I started my Roon journey by trialling the all-in-one solution on a desktop PC, then moved to a Roon Server running on a Windows 10 server, and have ended up with an Intel NUC with ROCK installed. I have Roon installed on a variety of PCs and tablets around the house controlling this Roon appliance and my audio endpoints. The system has grown into this.