A few years ago, I had those little pests climb UP wooden benches to get into my bonsai collection. I feel your pain.

Keep the floor of the greenhouse as clean and as free from debris as possible. You might even want to consider a gravel or heavy woven plastic weed cloth on the ground. Altering the environment as much as possible to make it inhospitable for these isopods will be very helpful.

You can try horticultural grade diatomaceous earth in your containers (and on the ground around the containers). The correct kind of DE can be found in most garden centers...just make sure that you don't get the stuff made for pool filters.

It's very important that you keep toxic chemicals out of the greenhouse. Insecticidal soaps 'might' be helpful, but I'd not advise a soil drench with it. I've found that those products alter the consistency of the soil, even potting medium.

In the future, you might want to place your containers within a structure (like a large tray or wooden box) that you can layer with perlite. The perlite will prevent those critters from gaining access to the plants.

Pill Bugs, Sow Bugs, Wood Lice, and the other 1,000 names these normally beneficial insects are called need a moist environment to exist. Drying out where they nest, hang out, is the best and simplest way to control them. A gravel or stone floor makes a very good living and breeding environment for them because that will be cool and moist and be just what they want.