Help with basic Roku and when to cancel Dish

It's free, but don't expect to get everything you were getting with Dish for free.  If you have a subscription to Netflix, you should be able to just launch the app and sign into your account.  Most here would recommend always bypassing 3rd parties like Roku when subscribing to any service.  Subscribe directly with the provider to avoid headaches when a billing/subscription occurs.

To get local channels, the easiest and cheapest way is to connect an antenna to your TV and see what you can pick up.  That will be totally free.  Sites such as AntennaWeb can help with what kind of antenna you need and where to point it.  If an antenna isn't feasible, then you'll need to subscribe to a streaming service that provides your local channels.  The following page is a bit dated, but still provides good information:

6 cable alternatives and live TV streaming services (2022)

You can find plenty of free ad-supported (or ad-inundated) content on apps like Plex, Tubi, and "The Roku Channel".  Cancel Dish when you've decided that you can live without it.

Since you're new, keep in mind that Roku is free and you can even remove your payment method if you don't plan on subscribing to anything through Roku.  Roku support is also free (and right here is where you'll probably get the best answers).  Beware of scams!  If you're not sure if something is legitimate, ask here.