Anderton

Sanderxpander
I didn't in turn mean that to be an attack. But I saw a few comments in the spirit of "Sonar is fine for EDM if you know how to use it".

Well...I'm not sure everyone involved in this discussion knows the following. Although you don't have as many options as when copying (e.g., you can't choose to copy into an existing pattern) I think the following does exactly what the OP wants, with the only difference being that you need to create your pattern in the Step Sequencer (which has its own advantages anyway) and not the PRV:
 
1. Create your pattern in the step sequencer (this creates a clip in the track view).
2. In track view, click-drag the clip edge to roll the clip out for as many iterations as you want (note that the Step Sequencer will still be available in the dock). You don't have to convert to a clip, convert to a groove clip, or anything. Just roll the sucker out.
3. Any edit you now make in the step sequencer will be reflected automatically in all the iterations you rolled out, just as if all the iterations were linked. You don't have to roll the iterations back in or change anything, just access the step sequencer and make your edit.
 
Even better...suppose you're not a fan of cookie-cutter repetition, so you want to make changes in some parts of the sequence, but not others. You can then bounce what you have to itself, create a clip, and edit it in the PRV, or convert the longer clip into a longer step sequencer pattern. 
 
I get the sense that the step sequencer's humanizing and editing capabilities are underappreciated because it's assumed SONAR's step sequencer works like most other step sequencers. However once you dig into what happens when you expand a row, it's pretty amazing.
 
But there's another point worth mentioning. Not all EDM is MIDI-based; my heritage is the MPC sample-based mentality that existed long before virtual instruments. Although there are programs that may have "better MIDI workflow for EDM" than SONAR, where many (most?) of them fall down is the audio workflow for EDM. For that type of work, I greatly prefer SONAR, and MIDI techniques like the one above can be found with a little digging.
 
What I find confusing about comments like "this or that program is great for EDM" is that in my experience, the programs that are referenced are good for a specific EDM workflow around which the program is optimized. That's fine and makes a lot of sense from a design standpoint (which is why I use Live for live performance), but it can preclude a more general-purpose approach that allows going beyond the boundaries of the program's design philosophy. For many people that may not be necessary, but for others, it is. For example it was really interesting to see how Ilan Bluestone creates his EDM projects in SONAR when he gave a workshop with Jimmy Landry at the 2015 GearFest. SONAR was able to accommodate the unique workflow he uses; I'm not sure what other program could. Same situation with me...

scook
Rolling out a clip usually refers to grabbing the end of a groove clip and dragging it. This causes the clip to repeat. In this case, instead of replicating a groove clip, the clip repeats the pattern in the current step sequencer instance. Changes to the step sequencer are reflected throughout the clip.

RedSkyRoad
I don't understand what you mean by "rolling out"