Hard to say without seeing a screenshot or something, but somethings I might speculate are that with your materials being non reflective, Unity uses a glossiness(smoothness) map instead of a roughness map which are basically inverts of each other. So if you created a roughness map that was very dark, meaning smooth, and you import it into Unity to use in the smoothness input, it's going to show the opposite of what you intended. So if that's the case you just need to invert the map before you import it into unity.