Washed stone taken from roof, is it safe for landscaping?

If it looks clean I'd go ahead and use it, but not on veges or edibles.

In my area, there are no roofs made with round stones of any size, so I can't comment on how they are put together. It might be helpful if you talked to someone in your area who knows how that sort of roof is constructed and maintained, that'd be your best guide on if there's something you don't want in your landscape.

Lucky you! Round, natural stone is beautiful used in landscaping. I doubt that they are contaminated since they've probably been rain washed for years, but if you're in doubt, just don't use them near any culinary plants such as vegetables or herbs.