>>12245919CS, robotics, and mechanical engineering all intersect at...well, robotics. There's mechatronics, control, motion planning, etc.., which take nontrivial contribution from all. At some point, you will learn all of these things.
If you're comfortable with pure mathematics, you can afford to go CS, focus hard on motion planning and topology, and pick up the mechanics pretty easily - it's not as hard as it is involved. Otherwise, if you feel like you really need school to teach you the classical physics and some of the math, do engineering school with mechE as focus.
