I believe in this area if the supervisor is unable to his job, debilitating health issue/resigning, the clerk becomes the acting/interim supervisor. In regards to your bill issue. The road commissioner has this in his approved budget as a line item. Any bill submitted by the cutoff date is processed at the next board meeting. As long as there is a "quorum" of trustees they can vote to approve payment of bills and other business. The trustees can also vote to have the clerk/interim supervisor maintain that position until the next general election or the trustees can nominate and elect  one of the existing trustees to the supervisor position until the next general election.