Not the OP but the owner was probably doing any number of tasks required to run a company other than driving nails on a roof. . ie. Doing estimates, arranging for materials, bookkeeping, etc.
Managing crews of workers - but I see ownership and management as work, as I am myself a business owner and manager of many people. But some would argue management is somehow not "real work" even though I've been pulling 70 hours a week for years!
I've done quite a few roofs in my day and managed crews. If someone is "managing" without getting up on the roof, they're not doing the real work.