I don't see anywhere where Roku say they will (or will not) process payments on a specific day of the month, but I do find where they say: "You are responsible for any over-limit, non-sufficient funds, or other overdraft fees that your payment method may charge you as a result."
So, I would suggest either keeping an extra $10 in your account at all times (allotting $10 once certainly beats losing $35 each and every time this happens!), and/or use a credit card instead of a debit card (gives you a little flexibility on exactly when to pay – but don’t go overboard and end up paying interest on TV!) or find a bank or credit union with lower fees. Interestingly, in many cases if you DON'T select "overdraft protection", a debit is declined and there is no fee. If you do select it (and it may be the default), the debit goes through but you get a fee.
By the way, Ally Bank says they have no overdraft fees. (Just as an example, I have not used them.)