I don't know whether a semicolon or a comma should be used. For example:
Now that GoT is done for the season what will James complain about besides Disney movies?Find out on a new episode of Off Time Radio; if he ever texts me back.
I would use a comma in this case.
A semicolon should only be used when the clauses you're separating can stand on their own as complete sentences. In this case, "Find out on a new episode of Off Time Radio" is a complete sentence, but "if he ever texts me back" is a dependent clause and cannot stand by itself. Thus, it would be incorrect to use a semicolon here.
It would also be incorrect to use an em dash or period for the same reason. These serve the same grammatical function as a semicolon but imply different types of relationships between the joined sentences.