Well,
The way to find out if your module loaded is to run lsmod
lsmod | grep rotary
for example, will list any mods already loaded and contain the name "rotary".
If its there, after your insmod you can rest assured it’s installed correctly.
This does not mean however that our little configuration line bus0= was correct necessarily.
After loading it, run dmesg, perhaps grep that too for " rotary" and look in syslog for any output it may have logged, such as errors.