PURPOSE: To prevent the roll from being injured during its replacing work, by interposing a water-soluble sheetlike material between the contact surfaces of two rolls in order to protect these contact surfaces.

CONSTITUTION: A lower backup roll 1, an upper backup roll 1', a lower work roll 3 and an upper work roll 3' are built in a rolling mill for serving in the rolling work; now, in these rolls, the lower work roll 3 is required the replacement because of its surface being worn out. In this case, the upper backup roll 1' and the upper work roll 3' are first pulled up, and next the lower work roll 3 is removed away; after that, a water-soluble sheet 5 is put on the upper surface of the lower backup roll 1, and then, a new lower work roll 3 is laid on this sheet 5. Hereby, if the lower backup roll 1 causes a slip against the lower work roll 3 during the roll assembly is being transported, the surface of these rolls is not injured. After replacing the roll, if the cooling water is sprayed on the roll surface prior to starting the rolling mill, the water-soluble sheet 5 is dissolved into the water and is removed away. As the water-soluble sheet 5, water-soluble paper or film is employed.