The OKC Thunder, with the addition of Tari Eason, would get better at rebounding and even better on defence, whilst still being a decent stretch-4.
I do not believe the Rockets are quite yet ready to compete for a championship, so with Ousmane Dieng, they gat a young player that might develop. The Rocket also get a first round pick and a second, the former of which will probably be in the 20's. They can use these picks either too draft or as an asset in a bigger trade in the future.
I am not sure if this trade is fair, but I do think Tari Eason could be very good with the Thunder.