A roll of stamps usually contains 100 stamps. The way to know how much is a roll of stamps worth is to multiply the value of each stamp by 100. For example, if the roll of stamps is for current first class stamps which cost 45 cents each, a roll of 100 stamps would cost $45. If the roll of stamps were one dollar stamps, a roll of 100 stamps would be $100.
The cost of postage stamps keeps going up. This can lead to confusion about what the current rate of postage is for a first class letter. One way to avoid the confusion, and to avoid sending a letter with an old stamp that no longer covers the cost of mailing a first class letter, is to buy forever stamps. A forever stamp will always cover the cost of mailing a first class letter up to one ounce in weight, even if the cost of postage goes up in the future. This is true even if the stamps are bought in a roll of 100 stamps.
Regular stamps have their value marked on them. A forever stamp does not have a value marked on it. This is the way to tell if a stamp is a regular stamp or a forever stamp. Buying extra stamps to cover the cost of postage rate increases can be a hassle. Forever stamps are a good way to avoid this hassle and be sure that you have correct postage on a letter.