Why is this important?
The panels will actually produce different amounts of power when they are facing different directions. When a panel is facing true south, it will receive more sun than a panel facing east. This is important to consider when designing your system. Even though you may not want the panels on the south side roof, keep in mind this will be the highest producing face on the roof! West is the next best option, following with East, and then you usually want to avoid the North face.
If you are mounting to a flat surface it is important to put the panels on tilt racks that will give them a better south facing angle. This will make sure you are getting the most out of your solar systems production.
The other thing you want to consider are any obstructions or branches that would be blocking sun light and causing a loss in production. Trim or remove any trees that will give you shading on your solar, and be aware of chimneys and satellite dishes.
Remember, the south is the best direction to face. It is ok to see your solar when they are saving you and the planet the way they do!