Why is my 2001 altima idling high and rough?

For the high idle, you could have a sticking fast idle cam, a faulty Idle/Throttle Speed Control Unit, or faulty Electronic Idle Speed/Throttle Actuator. You just may have some codes set. Is the Check Engine (SES or MIL) lamp on?

The rough idle should be evaluated at the same time. I'd recommend a shop that specializes in drivability conditions like those you describe.

Here's a link to an article on how to Diagnose a high or rough idle