A slanted roof would likely be a steel frame on top of the building, like the Ritz's, but also like what they're doing with the roof already. The steel and glass fins are a non-structural, decorative addition that happen to create the illusion of a flat roof rather than a slanted roof.
My point being that the fins, along with the extruded facade, suggest that Tridel isn't being cheap with the design; rather they've decided that a slanted roof (or some other "unique" design feature) isn't the route they want to take. Perhaps our skyline will continue look "boxy", but the growing sentiment that developers and architects are being cheap is unfounded. If anything, the non-standard floorplate that will result from the protruding facade, as well as the aforementioned fins, will be just as complex as building a roof that isn't flat.