No, you can only group/ungroup Sonos One speakers with the old Connect:Amp. 

Assuming they’re both running the same operating system. S1 devices can not be grouped with S2 devices. 

Those are powered speakers - how are you using them with Connect Amp?!
 

They’re plugged in.  They work great with the Connect Amp.

How have you wired them? The Connect Amp has only speaker terminals - the KKR should have only line level input jacks, right?

I just plug the speakers into the back of the Sonos Connect.  Maybe this is different from the Sonos Connect Amp?

Hi

That’s a Sonos Connect and not a Connect:Amp (See picture below). FYI, the Connect has been replaced by the Sonos Port.

You cannot “directly” connect (i.e. plug-in via RCA cable) any Sonos speaker to the Connect nor Connect:Amp. You can Group a Sonos speaker with the Connect and the KRK Rockit speakers will play the same music.

Likewise you cannot Pair a Sonos speaker with the Connect nor Connect:Amp. Pairing requires two Sonos speakers of the same type which create a stereo pair. For example:

• Two Fives
• Two Era 300’s
• Two Era 100’s
• Two Sonos One’s 
• Two Play 1’s 
• Two Play 3’s 
• Two Move’s *
• Two Move 2’s *
• Two Roams

 * A Move and Move 2 cannot be paired 

So it is a Connect not Connect Amp. The Connect has two outputs - the analog ones that the KKR are wired to, and the unused digital outputs that can be use to add another speaker/speaker pair that will take digital inputs. Via the right kind of cable. Such a speaker will have to be a third party one - like the KKR, but one that has a digital input jack.

Thanks.  Can I at least create a group using the Sonos Connect / Rokit speakers, and the two paired Sonos One speakers?

Yes, you can. Group the Connect with the Sonos One stereo pair.