I should not be responding as I am not a builder…will take a guess here, which will also get you out of the “nonanswered” category.

Truss?

"This image is from a roof project being constructed with wood trusses. As you can see within the red rectangle, everything is uniform, sturdy and well constructed. Here you have a solid roof structure that wasn’t “sticked” together. Instead, the roof is much more stable, strong and durable."

So, are you saying that you want to vault the ceiling in the center of the house - the original part? Or are you trying to vault one or both of the ceilings in the areas that were added? The roof of the addition is overframed - meaning that it sits atop the original roof and it is structurally tied into the original roof.

Regardless of which area you are trying to vault, you will have to build a lower vaulted ceiling in - you cannot attach the ceiling to the original rafters. You can't get enough insulation in to meet code unless you build down to create a space for insulation between the vaulted ceiling joists and the rafters. The two added areas don't have enough pitch to the roof to bother trying to vault. It would be a waste of money. The center section might be possible.

No way to even estimate cost until all the engineering is done and a plan is developed - but it will be significant. Once you touch it, everything has to be brought up to today's codes.

I plan on spray foaming the roof so that I don't have to build it out to accommodate for fiberglass insulation

It'll cost a fortune to do this right. Think about another house.

it's on one of the highest rated lakes in the Midwest. once I reframe the roof and spray foam it, the entire roof will get lifted off and set to the side while a garage is added and a second floor is built over the entire structure. it will then be re-set onto the new framing

David: speak with your builders doing the garage about your plans. It makes no sense to me (unless I’m not comprehending your description) as to why you would redesign your roof, then lift it off for a garage and second floor addition. It’s not like building a house with Lego’s. Talk with your builder and have everything done at once.

Will your foundation support a second floor?

I am working with a GC. Several GCs have recommended lifting the roof of and resetting it. the section of the house near the lake is a converted porch on a slab, so I can't put a second floor on that portion of the house without a considerable investment. the rest of the house has a relatively new basement under it. The GC inspected it and said we are food to go.

thank you everyone. I think I am going to hold off and just build a new roof when I add the second floor. still need to do a little reframing so that I can add a recessed beam and remove the old exterior wall to open up the inside a little more.