Why not both? You only live once, might as well dive in and enjoy the whole bag of goodies. As Drakan said, the Fable series becomes more simplified overtime, but you can still do roleplaying in it. Peter clearly wanted to make the series open-world, but for one reason or another just never managed to achieve it, but the sequels are still fun by their own merits. Your character can't talk except for in Fable 3, relationships in the game aren't that deep, you can get a spouse just from farting a few times after all. The series as a whole for lack of a better word is unique, you can't go wrong with the series, the only downside was Peter Molyneux's failed promises, ignore those promises and you still have great games.
If you want the best of both worlds for Fable & Oblivion, then shoot for Kingdoms of Amalur it's an excellent game that sadly didn't get the justice it deserved (ended up getting eclipsed by Skyrim). If you're in the market for more open world games like Oblivion, then go for Fallout 3 & New Vegas same engine, gameplay and developers (though NV is by Obsidian). You can also do Morrowind if you haven't given it a try, arguably the best Elder Scrolls game period. Oh, and Daggerfall (some DOS respect)
The original Dragon Age is good, but it was also rushed, especially the console ports which are buggy and have performance issues (DA2 is polished however). If you're going to get it, then either get it for PC or settle for the 360 version. Alternatively, you can go for Bioware's Mass Effect series instead, same roleplaying depth, but with guns and intergalactic fun. Neither of them are open-world like Inquisition or the rumored Mass Effect 4, but their deep story-driven gameplay is superb. Honorable mentions with Jade Empire & KOTOR.
I too also recommend the Witcher series, including the new 3rd one which looks amazing so far and unlike its predecessors is open world. Although with the Witcher series you don't get to create your own character like with the other games mentioned, still awesome though.