Midwood Yid, you are allowed one personal item such as a rolling suitcase, purse or laptop bag. Depends on who checks you in determines if they weigh it or not.
RebYidd23, a carry on can be upto 10 or 12 pounds. If its more they will make you check it in. If u already have a checked in bag you will have t pay. Sometimes these rolling carry ons are so heavy that they take up most of the allowed weight.