This is a good question. Technically, none of them do. However, there needs to be distinction between the continuation indicators and the roman numerals. The suggested practice is to put the grade 1 indicator between the lettered continuation indicator and roman numeral.
You say "technically" but then add "distinction." If technically correct why a distinction? Braille 2000 UEB version WILL NOT let me add the gr.1 indicator in any way I know of (unless perhaps I do a "Page Numbering Layout" for each page, which is very tedious for 70+ p-pages). It appears that Braille 2000 takes "technically" to mean that "letter signs" are not necessary and will not allow the "distinction" to be made. This could be problematic If I submit volumes w/o the indicators and proofreaders say they are needed, I won't be able to add them and will have to stand on the argument that "technically they are not needed."