Strawbery rhubarb crumble in ramekins
From thawed, definitely. Reheat until warm and bubbly. Yum.
I've done both (from frozen and thawed) but with apple crumble. If you bake from frozen, I'd suggest covering with foil for a while while it's baking so that the top doesn't brown too much. The risk of thawing first is that your topping gets too soggy to crisp up in the oven.
I second on the bake from frozen. Although, you may not be able to prevent the bottom from getting soggy, you may be able to minimize it. Try baking on a preheated sheet pan or pizza stone.