Sassafras Roots song meaning

Sassafras is one of the main ingredients in root beer, so the title of the song might be referring to the consumption of that drink.

The narrator's words are directed towards a friend or someone that he wants to spend time with. He points out that this person does nothing but waste their own time all alone, and offers them to waste time together. "When I'm a waste like you, with nothing else to do, may I waste your time too?" - this is basically an odd way of saying "May I keep you company?"