i have not joined rokutv; i don't plan to unless NECESSARY
i did not have to join roku to add netflix to my system; functions perfectly
can i just contact hulu, sign up with them ?
Not sure what you mean by "joining" Roku. To set up a new Roku, you have to have a Roku user account, which doesn't cost anything. Roku themselves offers nothing that requires a subscription. You can subscribe to some providers through the Roku channel. But you have to have a Roku user account of some kind, or you can't complete setup.
You can download almost any channel from the Roku Channel Store for free (there are some screensavers that cost), but some do of course require a subscription, such as Netflix or Hulu. Yes, contacting Hulu and paying them for a subscription would be required to use their channel on a Roku player.
Just to clarify a bit: For most channels that require a subscription, you do NOT have to do it through Roku. Most will let you sign up directly (usually through their web site), then just log in the first time you use it. Unless you really like to have just a single bill, I'd recommend that method. It removes a middle-man that can cause billing issues, and the service gets 100% of your money instead of Roku keeping part of it.