Prevent roots in open compost pile?

I normally use a rotating drum for compost. Soil test results show I should stop adding organic matter to the soil for the time-being. I need to start an open compost pile, as my drum is full. My husband reminded me that once when we had a big pile of leaf mulch, the maple tree roots grew up into it and we ended up with a root-bound hillock. Any thoughts? All my potential locations are near maple or oak trees.

tamarmays - I have a huge oak tree in my garden, and each year I have to cut roots from my raised beds. Trees know a good thing, and compost piles are like "Sunday Dinner" to them!