I would pronounce it like it was a combination of the names [name_f]Rose[/name_f] and [name_f]Amelia[/name_f]. [name_f]Rose[/name_f]+elia of [name_f]Amelia[/name_f].
I’d pronounce [name_f]Rosalia[/name_f] and Rozalea same, but different from Roselia.
[name_f]Ros[/name_f]-EH-li-a, kind of dragging out the second syllable. I pronounce [name_f]Rosalia[/name_f] the same as Rozalea (as above) though I prefer [name_f]Rosalia[/name_f]. In Roselia, the second syllable is more accentuated.
Roselia: rose - uh - [name_u]LEE[/name_u] - a - Sort of like [name_f]Rosalie[/name_f]-a
[name_f]Rosalia[/name_f] - rose - UH - lee - a - Sort of like [name_f]Rose[/name_f] - [name_f]Aliya[/name_f]
[name_f]Rozalia[/name_f] - roz - uh - [name_u]LEE[/name_u] - a - Sort of like [name_f]Rozalie[/name_f]-a
I think it would need to be spelt [name_f]Rosalia[/name_f] for me to pronounce it [name_f]Rose[/name_f]-uh-lee-uh if that’s the pronunciation you are after.