I don't see any other way than removal. Putting a new roof on top of a bad one may work for shingles but not here and especially with the tar bubbling.
I can't see it to be for sure, but you probably should remove it and maybe you can reuse the stone if you so desire. Even if you put on a wood deck an inch or two above the old one, you best fix the roof now before you have to tear off the new and the old to fix a leak next year. good luck.