What should you do? Check the weather forecast. If warm weather is coming, the snow will melt on its own. If not, you should remove the snow to prevent damage and ice dams from forming. Ice dams are a build up of ice along the edges of the roof that prevent water from properly running off the roof. This can cause water to seep inside instead.
There are two ways to remove excess snow from the roof. The safest way is to hire a professional. They have the knowledge to remove snow without damaging the roof and the equipment to do it safely. If your roof is lower and you can reach it from the ground with a long handled rake, you can try to do it yourself. Many home improvement stores carry special snow removal rakes for this purpose. They are still difficult to work with on very heavy snow. Be careful not to stand directly under where the snow will fall from the roof. You should start at the bottom with the overhangs and work your way up going about a foot at a time. Be sure to watch for dangers such as power lines hanging near the roof. Remember the goal is to remove the excess snow, not all of the snow.
If you need to get on the roof and shovel the snow to remove it, it is best to hire a professional.
When the winter snow comes, consider the effect it has on your roof and take the necessary steps to protect your investment.