Not quite.
If your total load was 17 ohms, it would draw 700 mA at 12 volts.
Presumably your load requires 12 volts, correct? If you put a resistor in series with a 12-volt power supply, the load will get less than that.
I'm not sure what you have, but I think I'd figure it this way:
Your load requires 12V @ 700 mA. If you need a series resistor to limit current, obviously you'll need > 12V supply. Get one, or assume the voltage. Let's say 15 volts.
You want the resistor to drop 3 volts (15-12 = 3). So size the resistor to draw 700 mA at that voltage:
R = 3 / 0.7 = 4.3 ohms.
By the way, are you sure you need to limit the current to your load? Some devices (notable LEDs) require current limiting, while others, like most motors, do not: you can just let them draw what they want to draw. What is your load?