edit- I no longer believe that anything contained in this post helped at all, other than finding out how to add a new controller profile to MAME32. See below.
I was having the same trouble with MAME32 0.76- I found that I had mouse control in games with input type trackball, but not in games with input type dial.
Here's how I fixed it:
In /mame32/ctrlr there are .ini files for custom controller layouts. There's a std.ini file in that dir that's full of all the default options. The relevant part is pasted here:
P1_DIAL "KEYCODE_LEFT | MOUSECODE_1_ANALOG_X"
P1_DIAL_EXT "KEYCODE_RIGHT | MOUSECODE_1_ANALOG_X"
P2_DIAL "KEYCODE_D | JOYCODE_2_LEFT"
P2_DIAL_EXT "KEYCODE_G | JOYCODE_2_RIGHT"
P3_DIAL "KEYCODE_J | JOYCODE_3_LEFT"
P3_DIAL_EXT "KEYCODE_L | JOYCODE_3_RIGHT"
P4_DIAL "JOYCODE_4_LEFT"
P4_DIAL_EXT "JOYCODE_4_RIGHT"
P1_DIAL_V "KEYCODE_UP | JOYCODE_1_UP"
P1_DIAL_V_EXT "KEYCODE_DOWN | JOYCODE_1_DOWN"
P2_DIAL_V "KEYCODE_R | JOYCODE_2_UP"
P2_DIAL_V_EXT "KEYCODE_F | JOYCODE_2_DOWN"
P3_DIAL_V "KEYCODE_I | JOYCODE_3_UP"
P3_DIAL_V_EXT "KEYCODE_K | JOYCODE_3_DOWN"
P4_DIAL_V "JOYCODE_4_UP"
P4_DIAL_V_EXT "JOYCODE_4_DOWN"
There are folders in that dir for SlikStik, Hotrod, and others. Each has a default.ini file in it, and some have other game-specific files. I created a folder named OptiWiz, and then created a file called default.ini in that folder.
I copied the entirety of std.ini into the new default.ini file, although I could probably have just used the lines I changed. I changed the first two lines of the dial section:
P1_DIAL "KEYCODE_LEFT | MOUSECODE_1_ANALOG_X"
P1_DIAL_EXT "KEYCODE_RIGHT | MOUSECODE_1_ANALOG_X"
and then went into the options menu of MAME32 and clicked "Default Game Options". On the controllers tab, there is a spot to change the default input layout. OptiWiz is now one of those options! I chose it, and then fired up a game of Tempest, which previously wouldn't allow me to use the mouse- and it works! I've got my Blasteroids spinner hooked up to the X-axis and I am good to go. I haven't messed with the other dial inputs, but it looks pretty straightforward.
Hope this helps.