Waaaaaay back in the day, pre-80's would be a rough guesstimate, nobody ever heard of trusses. Homes were stick-built and stick framed of standard dimensional lumber. Homes with walkable attics (which were eventually finished into rooms) and garages with actual space above them were common. A floor joist and a ceiling joist were one and the same.
Since the development of truss systems, and the push towards impressive, wild voloputious soaring rooflines, your ceiling and roof and the walls below that support them are no longer separate things, which one can alter. Your roof support and ceiling support, are one and the same thing. To alter ANY of it, requires that the entire space be completely redesigned and resupported. You cannot just waltz into a trussed attic space or a vaulteds ceiling space and hack out anything that gets in the way of your new plan. Your roof needs the ceiling and your ceiling needs the roof. And depending on the particular design, your roof and ceilings may be depending on a lot of other things that would suprise you.
The first step in redesigning any engineered truss space is a licensed architect. This is not DIY stuff.