Hi,
I have a Hulu Disney plus subscription,
do I need a Roku subscription as well?
do the channels overlap?
There is no Roku subscription per se, though Roku allows you to create and/or access many subscriptions through it. It also allows completely free viewing of many services, though typically with many commercials.
Be careful when accessing a subscription on a Roku (or other device) to sign IN to your existing subscription and not sign UP for another subscription.
To expand on what @Strega2 said, if you already have a subscription to a provider like Disney, MAX, Hulu or other services, no you do not need a separate subscription to view that provider using a Roku device. I have subscriptions to MAX and Prime Video, neither of them through Roku, and I can view their content on any of my Roku devices or my other streaming players as well.