Roleplaying in D&D, as in any other setting, including Shadowrun, is a function of the interaction between the DM and the PCs. The dice are there because not everyone has the silver tongue of a bard, or the nimble fingers of the rogue, or the fighter's skill with a blade. The diceless systems are no better or worse at roleplaying. Indeed, I've seen more than a few such 'diceless' games devolve into cowboys and indians style shenanigans.
And where, then, is the "roleplaying as a key aspect" in Shadowrun? The 1-2 karma points you may get for good roleplaying if the DM feels like it, just like how a DM in D&D can award bonus XP for roleplaying if he feels like it? I will admit that D&D books don't have the same flair as Shadowrun books do, but there is a simple reason for that. Shadowrun is a single setting. D&D is designed to be used in different settings, be it Greyhawk, Faerun, Ravenloft, Eberron, Dark Sun, Dragonlance, Birthright, or any one of the hundreds of thousands of homebrew settings that DMs have brought in over the years. Shadowrun's system is intrinsically tied to the setting, making it far more difficult to transplant into another world than D&D, which provides a skeleton, and allows DMs to put meat on the bones, building the world to their specifications.