I can use multiple zones with Roon, Alexa, Sense and other services.
I can create groups with both Roon and Alexa, but Alexa has advantages over Roon as:
In Roon, when items are grouped, they can only work together. With Alexa, the group is separate and the zones can still operate separately. With Roon, a zone has to be removed from the zone first.
In Roon, grouped items do not have equalised volume levels, or the choice to equalise. In Alexa, a group effectively works as a single larger zone with one volume level.
The ground floor of my house is mostly open plan so I have 5 zones. Sometimes might just want to have the radio playing in the kitchen area, other times absent music everywhere. If there kitchen is grouped, it first has to be detached. Having to equalise volume manually is a pain.