Can you control the angle of a continuous rotation servo?
If you're talking about a modded R/C servo, no, you can't.
It isn't really a servo anymore - no feedback.
How do you control the speed of the servo?
Pretty much, you can't. There may be a small amount of control either side of the null position, but it is usually quite load dependent.
Experimentation. If you try timings which would put the servo at 90 degrees (depends where the pot was left or how well-balanced the resistors are), you should find a point where it stops. Use the "writeMicroseconds" method for fine control.
(depending on Servo library version, you can write the pulse lengths directly to the "write" method too)
Is the Servo.h library meant for continuous rotation servos too
You can use it, but they're not servos anymore, they're geared motors with a single wire direction control.
Could you guys post some code meant solely for continuous rotation servos
You need to experiment for yourself - any values we give for the stationary point may well be off for your devices (and your devices themselves may all be different).
If you wire up a pot, and map the 0..1023 range to something like 544..2500, use these values as parameters to "writeMicroseconds" and print them to the serial, you should be able to get close to the null position pretty quickly.