I can't see why Anthony Morrow is slipping out of OKC's rotation. The rationale for starting Roberson is pretty clear -- OKC isn't in need of major offensive production with their big 3 (plus Kanter) healthy, and he certainly resembles Thabo in his defensive abilities.
Less understandable is Waiters getting the lion's share of backup minutes at SG thus far under Donovan. Waiters hasn't proven jack. In contrast, Morrow finished 12th among SGs in RPM last year (2.76), in large part due to a ORPM (2.33) but was still positive on defense (0.43).
He's not exactly young (30), but is absolutely a dead-eye shooter ... a major need for us (e.g., we beat WASH handedly when we shoot unsustainably well as a team, but could lose to almost any one when we don't). He shot 43% from 3 last season, averaging 4.4 in ~24 mpg... and he finished the season strong.
Morrow seems like he could help fill a void for us, he's non-guaranteed next season, and on contract for 3.4 mil/ year (basically the same as Turner). I'm viewing this as another marginal improvement as we wait for a greater opportunity (if it comes). Unfortunately, I'm not sure we have anything to offer OKC (without overpaying) to make the deal happen. And admittedly, there well could be something I'm missing here, given he's riding the pine behind Waiters right now. Just seems like a good fit for our current needs, and isn't the type to age poorly.