Not sure how effective that would be as you have to remember that by multiclassing you are giving up potential in both cllasses...by taking 3 levels of rogue you give up 3 levels of sorcerer and spellcasting really isn't what the rogue is about. And a level 3 rogue really isn't much of a rogue at all. The only positive I can see is if you take rogue as your first class at level 1 you can gain a lot skill profficiencies for a more effective skill monkey but that's about it. But yeah...not great for gameplay. I'd rather stick to pure rogue or pure sorcerer and leave what you can do to another class. The positive is both Rogue and Sorcerer are great face classes in their own rights and being the face of the party is the only role companions can't properly fill.
Thief gets 2 bonus actions. Metamagic allows for spell casting as bonus actions. This build could cast 3 spells a turn and do cool things like Misty Step twice in one turn. It’s a good build idea.
