roller guide 1 is provided upstream of each of the roll pairs 14 16 18 and 20 i e the roll pairs that roll the rod to a round shape alternatively one such roller guide can be provided at each roll pair in the rolling line all of the roller guides 1 will conveniently be provided with vibration measuring means that enable the inventive method to be applied the rolls of respective roll pairs can be adjusted relative to each other in a known manner such as to enable the distance between the rolls of a respective roll pair to be either increased or decreased because of wear on the rolls on the one hand and also because of differing qualities of the material to be rolled on the other hand when the vibration measuring means are used to monitor the state of the rolls vibrations occurring in the arms 7 and 8 of the roller guides are analysed by frequency analysis in the case of frequency analysis vibrations deriving from normal rotation of the rolls the frequencies of which can be established when the speed at which the stock is advanced and the width and diameter of respective rolls is known can be sorted out from the analysis and changes in other selected frequencies can be used as a measurement of the load on the roll pair concerned frequencies deriving from other control points in the rolling line or rolling mill can.