I used green-coated OSB for the roof of my house, and I can say that the material gives good tightness if you glue the joints correctly. But unlike the walls, on the roof, moisture load and temperature differences are higher, especially if vapor permeability is important. I have personally encountered that without good ventilation in the covered space, it begins to accumulate, especially in winter. Suppose there is no possibility of making a full warm roof. In that case, I advise that everything be carefully calculated to ensure the dew point and provide at least minimal ventilation; otherwise, sooner or later, the tree will start to get wet.