"Note: In Guest Mode, you cannot make purchases that are billed to your host's Roku account. You can however make purchases when you sign in to a channel where you have a payment method on file."
So it sounds to me like the answer to your question is yes if they already have, or establish, an account to say Redbox and set up a payment method directly with them. It would be completely separate from any Roku account.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution." If you appreciate my answer, maybe give me a Kudo.