good rolling technique should be independant of you paddle blade. a good roll should be made of good body technique and less paddle.
kinetic shaped blades are excellant all round blades and every company has there version to go with. tempest shaped blades are good for forward strokes and support.
length is important. shorter gives less stability and power but qiucker strokes.
moral of the story try every thing before you buy.
H20 blades have plastic blades which i have seen break, rough stuff have developed a bad reputation on breakage. werner are excellant but pricy. robson seem quite solid.
for grade four plus paddlers, the strenght of the shaft is one of the most important safety factors when paddling. if you swim because you riped you deck off, well thats your problem, however if its due to your blades breaking you may get subjected to a nasty swim which was not your fault. remember that.