A north facing roof maximises the power output of your solar PV system, not all of us are so lucky to have a house running perfectly parallel to east or west. So what if your home runs north to south? Will you have to choose between morning light or afternoon light? To get a better idea of how the sun passes over your location check out the Sun Calculator.
It may surprise you to know, after all things considered, it can come down to whether the weather in your area is clearer in the mornings or the afternoons. Often the afternoons have clearer skies meaning a west facing system could generate a greater amount of electricity. On top of that, often peak consumption occurs in the afternoon. There is always the option to split your panels across the east and west face of your roof. This will give you the best of both worlds with consistent energy production throughout the day.
So in conclusion even if your roof is not north facing it is still worth getting solar!