As skiberger said, hire an structueral engineer. Some houses were not built for that kind of weight bearing down on the walls.
If you have a big roof, the weight of the a frame can push out on the exterior walls, causing the house to buldge, and possible collapse in on itself.
I would imagine you could achieve this if you left the ceiling joist in place, and just removed the drywall ceiling, then drywalled the upper part of the roof. I won't say this will look very nice, but maybe if your open minded, you can at least paint the joist, put some fake vines or something over them. Could look nice I suppose.
Also bear in mind that this will cause you heating and cooling bill to increase as your system has to work harder to heat/cool the extra cubic feet. Your system might not even be equipped to handle it.
All things to consider.
When you have a plan that you think will work and you can manage, submit your plans, and apply for a building permit. Planning departments are conservative. If they approve your plans, chances are it will be safe.
You cant go wrong with the above quoted advice.