Tidal is the streaming service, Roon is an overlay that adds better meta data and links to similar music it also integrates your own music you may have stored on a NAS for example. Like the others said you do not need Roon to use tidal. I don't use Roon anymore and just use the Tidal app on my PC.
some good suggestions already but for a lot more tech information and other ideas look at AudioStream.com its Stereophiles digital streaming sight. There is a huge amount of information there from the basics to more advanced set ups.
One other option is a small form computer ( Apple or PC) that has a digital out. I use an Asus Vivo, couple hundred bucks, but you do need a way to monitor it like a small monitor or if you have a TV in the same room makes for an excellent streamer and lets you do other computer related stuff that the dedicated streamers cant do.