I see after typing this you have had some success, and as suspected mono gives problems, but I’m going to leave all the below in as it might help someone else.
You should make sure you have the correct Vista 32-bit driver:
http://www.roland.com/products/en/_support/dld.cfm?PRODUCT=FA-66&iRcId=1812397&dsp=1
however one part of the site has a link to a PDF:
http://www.roland.com/products/en/_support/om.cfm?PRODUCT=FA-66&iRcId=1811006&dsp=1#
that says the driver is incompatible with Vista. You should contact Roland support to discuss this discrepancy.
If the driver is valid, it apparently supports both WDM and ASIO. Audacity as shipped does not support ASIO so it should only see the WDM stream. You should record from “EDIROL FA-66 In 1” which should be input jack 1 and 2 on the device. Keep it simple to begin with and set the Audacity project rate bottom left of the window to 441000 and recording channels on the Devices tab of Preferences to “1 (Mono)”. On the device, set the sample rate select switch to match (44100 Hz). From the Manual “If you switch the FA-66’s sample rate, you must turn the power of the FA-66 off, then on again to get the setting to take effect.”
You want to also go to the Windows system mixer:
http://wiki.audacityteam.org/index.php?title=Mixer_Toolbar_Issues#vistacp
select the device on the Recording tab > right-click > Properties, and look around for any settings relating to channels and sample rates. There will probably be a “Default Format” setting on the “Advanced” tab. You must set this to match with the Audacity project rate and number of channels, and with the sample rate selector on the device e.g. 44100 Hz mono. Make the same change from the Playback tab.
If you are only connecting one input and the input volume recorded into Audacity is too low, try recording 2 channels (make commensurate changes as required elsewhere) then close one of the recorded channels in Audacity.
If you still have problems, try the “DirectSound” host in the Audacity Devices Preferences.
Also note the Roland site says “A FireWire(IEEE1394) control chip from TI(Texas Instruments) is recommended.Please download and open fa66dv32_v105e.zip file then copy the fa66dv32_v105e folder onto your computer’s suitable directory. For the detail of this driver and the installation procedure, please refer to Readme_E.htm in the folder.”
Gale