Roeselare already has a Belgian sacch strain in the mix, so you'd just be wasting yeast if you used the WLP550.
As for racking off the cake; that is entirely up to you. Some people do it and some don't.
Primary: De Bom sour (Gen. 2), De Bom/Embrace the Funk Brett blend saison'ish beer
Secondary/Aging: ECY01 Sour #1, ECY01 Sour #2, The Yeast Bay Melange Sour, Bourbon Barrel Quad
In bottles: Mango sour, Lambic, Brett tripel, Sour brown, Brett L/B Porter
Kegged: Jamil's Sweet Stout with Raspberries, Dry-hopped sour (De Bom), De Bom on tart cherries