Collant problem

Take a good look at the coolant reservoir, it may have sprung a leak, check the radiator hoses. Also the thermostat housing, it is a 3 piece plastic unit that is glued together. The glue eventually fails, and youll start leaking coolant slowly or rapidly. Remember that coolant is under pressure and when it escapes rapidly it will make a sound and splash all over, so you may not now exactly where the leak is located. I suggest that you refill the coolant and run the engine at idle speed, then see if you can locate the area of the leak. There can be other causes such as radiator and water pump, but since you mentioned a "roaring sound", it could be among the ones I mentioned before.