I hear a roaring noise when I turn. - 2004 Pontiac Grand Prix

The noise would be coming from something that is turning at the same speed as the tires.
It could be a hub bearing or a worn tire.

find a live mech, to find noise, nobody here will ever guess cause.
we cant hear . nor use stereoscopic hearing to tell directions.

In my 2005 Nissan Altima I experienced a roaring noise from the rear of the car. It ended up being the rear wheel bearings needed to be replaced. It appears that this is a common problem with Nissan Altima's & Maxima's of varying years even with fairly low mileage. This might be your problem.

Is it possible you are hearing a wheel bearing instead of the engine or exhaust ?
Normally a bearing will roar on a turn and not on a straight stretch, but I guess its possible to do it the other way. A tire will make a roaring noise too.
I can't think of anything related to the engine that would roar only on a turn except maybe the power steering.

clicking noise from front end while spinning tyres is an indication of failing cv joints. especially while turning the wheel from left to right. Suggest you replace the shafts

Might be and sounds like a bad wheel bearing.

Most likely a bad wheel bearing in the front. If the noise is more pronounced when turning in a certain direction it is generally the opposite wheel bearing at fault (eg. turn left noise worsens, means right side wheel bearing). The reason is the weight distribution, when you turn left the front end engine and tranny weigh heavier on the right side, and amplify the noise.

roaring noise still continues after replacing driver side hub bearing

That roaring noise should be a wheel bearing. Jack up the rear wheels and spin the tires by hand. You can hear a grinding noise if the noise inside the car is as load as you state.. The only other noise that will be like that is the differental gears inside the drive axle

THIS NOISE IS USUALLY THE HUB. HAVE SOMEONE GO WITH YOU ON A TEST DRIVE. GET THE ROARING TO HAPPEN AT ITS LOUDEST AND GENTLY SWERVE THE CAR LEFT AND RIGHT. DON'T BE SURPRISED IF YOU THINK BOTH HUBS ARE BAD. LIFT THE FRONT OF THE CAR AND PUT IT ON JACK STANDS. PULL OUTWARD ON THE BOTTOM OF THE TIRE WHILE PUSHING INWARD ON THE TOP OF THE WHEEL. IF THE WHEEL MOVES EXCESSIVELY YOU FOUND THE HUB THAT IS NOISY. USING A MECHANICS STETHOSCOPE YOU CAN SOMETIMES HEAR A ROARING TYPE NOISE ON THE BACKING PLATE SIDE OF THE HUB WITH THE ENGINE RUNNING AND THE TRANS IN GEAR. TRY NOT TO GET THE SPEED UP TOO FAR ESPECIALLY IF YOU CAN HEAR THE NOISE AT LOW SPEED, YOU DON'T WANT TO VIBRATE OFF THE STANDS.