Joust has a single sound ROM on a separate sound board which is stored on a 2532.
There are at least 4 different ROM sets for Joust (most likely more since there is
a gap in the production numbering for another set).  The A" or "B" is the suffix
to the ROM number printed on the sticker labels.  The ROM at position F4, for
example, should either say "ROM 1A" or "ROM 1B" somewhere on it.  You can tell by
checking the checksums that a lot of the ROMs are identical but each set has
(at least) several ROMs which are unique.

The files are named in the following manner:  a prefix of the word "joust" signifying
the game name followed by a "."  and then a 2 character abbreviation of the sticker
color ("wr" for White with Red stripe, "sg" for Solid Green, "sr" for Solid Red, and
"wg" for White with Green stripe) and then a hexidecimal ROM number (1-C = 1-12).


<----------------------------Information from sticker---------------->
------------+  White/Red   | Solid Green |  Solid Red  | White/Green |
ROM | Board |   "A" 2532   |  "B" 2732   |   "A" 2532  |  "B" 2732   |
 ## | Loc.  |  joust.wr#   |  joust.sg#  |  joust.sr#  |  joust.wg#  |
----+-------+--------------+-------------+-------------+-------------+
 01 |   F4  | 16-30060-01  | 16-3006-13  | 16-3006-28  |    3006-52  |
 02 |   C4  | 16-30060-02  | 16-3006-14  | 16-3006-29  |    3006-53  |
 03 |   A4  | 16-30060-03  | 16-3006-15  | 16-3006-30  |    3006-54  |
 04 |   F5  | 16-30060-04  | 16-3006-16  | 16-3006-31  |    3006-55  |
 05 |   C5  | 16-30060-05  | 16-3006-17  | 16-3006-32  |    3006-56  |
 06 |   A5  | 16-30060-06  | 16-3006-18  | 16-3006-33  |    3006-57  |
 07 |   F6  | 16-30060-07  | 16-3006-19  | 16-3006-34  |    3006-58  |
 08 |   C6  | 16-30060-08  | 16-3006-20  | 16-3006-35  |    3006-59  |
 09 |   A6  | 16-30060-09  | 16-3006-21  | 16-3006-36  |    3006-60  |
 10 |   A7  | 16-30060-10  | 16-3006-22  | 16-3006-37  |    3006-61  |
 11 |   C7  | 16-30060-11  | 16-3006-23  | 16-3006-38  |    3006-62  |
 12 |   F7  | 16-30060-12  | 16-3006-24  | 16-3006-39  |    3006-63  |
----+-------+--------------+-------------+-------------+-------------+