A roll state monitor device includes: rolling force detector configured to detect rolling force of a monitored roll selected from an upper roll set and a lower roll set; force variation value extracting means configured to extract a rolling force variation value based on the rolling force for each rotation position of the monitored roll; and identification part configured to identify a roll eccentricity amount of the monitored roll by acquiring a plurality of accumulated values by accumulating separately for each rotation position of the monitored roll a value which is one of the rolling force variation value and a roll gap equivalent value calculated based on the rolling force variation value, and by dividing each of the plurality of accumulated values by a correction coefficient corresponding to a roll rotation amount.

A support roller, particularly for rolling mill systems or equipment for casting, conveying or straightening metal products, including a cylindrical roller axle, a hollow cylindrical outer ring arranged concentrically in relation to the roller axle, and a plurality of rolling bodies arranged between the roller axle and the outer ring. The roller axle further including a cavity, at least in certain sections between its central axis and a load introduction point. Due to the provision of the cavity the load rating and the service life of the support roller are increased.