I love your house and the bold choices! So lovely to see something different and fun. I'm also a fan of dark paint on houses. I like the color of the roof as it is now and would probably choose a dark roof. The gray you show on the blue house looks to be too cool to go with your paint color, which appears to have a lot of brown in it. So I dont know what other lighter color you could choose - a lighter brown wouldn't seem very attractive.
If this were my house, I would upload your pic to a roofing website that lets you try on roofing colors on your own home (if you can find one). Or even just a house paint website that has a visualizer and paint different colors on the roof to see what looks good.
Q