I've been known to assembly lasagne (vegetarian or otherwise) in individual serving dishes, which I wrapped really, really well with industrial style plastic wrap, then freeze. Worked fine and the individual portions were really handy. Just be sure and note the date of freezing.

You can buy some smallish foil pans and assemble the extras in there. Freeze it in those before cooking and you can take it straight from the freezer to the oven.