The question isn't whether arbitration clauses are legal the question is whether selling someone something and then, after the sale, presenting them with a take it or leave it EULA that disables the product if they dont agree, and also what recourse the consumer has if they don't agree to a post-sale EULA. Brower v Gateway said that post-sale EULAs are binding but only because in that case the consumer had the option to return the product for a refund and didn't. Klocek v Gateway ruled that any terms presented after a sale represent a separate contract beyond the one that was agreed to by both parties at the time of sale. It's possible that either of these would apply to the OP. It's also possible for courts to rule that the sale of the physical TV was a one-time agreement but that this EULA is separate and represents an ongoing agreement to allow access to Roku's services.

Your comment actually circles around the issue at hand when you say that EULAs are enforceable if "...you have been granted sufficient notice to accept or decline...". The thrust of the argument is that adding conditions after the sale of an object that, if not agreed to, render the object inoperable feels an awful lot like not being given sufficient notice and is essentially a backdoor by which the contract can be unilaterally amended after agreement.