Electronic kit recording

Since that Roland interface has only 2 inputs, you can only get a left/right audio mix from your electronic drums into Sonar and won't be able to achieve dedicated tracks of the kit's sounds. Even if it had more than 2 inputs, not every electronic drum module has individual outputs for each piece anyway. For example, the Roland TD20 drum module does, but the Roland TD-4 that I own does not.
 
If you want to record the sounds produced from your electronic set, just plug the left and right outputs from the drum module into the two inputs on your interface, You'll have to live with the stereo mix that it produces, because that's all you get.
 
That being said, with the gear you have, you actually can use the electronic kit to lay down individual sounds to individual dedicated tracks, but you'll need to do it via MIDI with software drums.
 
I'm always happier at mixing time if I have separate tracks for each drum and cymbal sound, so I never record the sounds from the module, and instead use the electronic pads via MIDI to trigger software sounds. To accomplish that, just plug your drum module MIDI OUT to the MIDI IN on your UA-25EX and make sure the UA is set up in Sonar as a recognized MIDI input. Then, open up a program like EZDrummer, Superior Drummer or even Sonar's built-in Session Drummer and trigger those sounds via MIDI to individual tracks.
 
Using Session Drummer as an example, when adding the soft synth to the project, checkmark "MIDI Source", "Synth Track Folder" and "All Synth Audio Outputs: Stereo" before clicking OK to Insert Soft Synth. That will give you an individual pannable stereo track for each piece of the kit.
 
Now, load the specific kit you want to use in Session Drummer. Then, to make sure individual sounds go to separate tracks, open the Session Drummer Mixer and assign each sound to a different track by changing the default "1" at the bottom of each slider to the number of the track where you want to send each instrument. You'll see list of choices when you click the downward arrow.
 
NOTE: If you make mixer channel assignments and then change the kit in Session Drummer, the darn thing will reset all of your outputs to "1". That's why I always make sure I've loaded the kit I really, really want before changing outputs.
 
Other drum software works pretty much the same way. EZDrummer and Superior Drummer make the mixer assigments a little faster, by giving the option to select "Multichannel" on the dropdown menu on the mixer page. When you select "Multichannel", the program assigns sound to different tracks all at once. (But like Session Drummer, it will reset if you change the drum kit!)
 
If you're not used to dealing with all of this, it'll probably be a pain for you the first time. The good news is, once you get everything set up, just save it as a Track Template. That way, the next time you want the exact same kit automatically set to individual tracks and ready-to-go, just insert your custom Track Template into a project. You won't even have to manually add the drum synth, because it's built-in to your Track Template! 
 
Like many things Sonar, once you get past the learning curve, it'll be a breeze.