The modernization options for the heavy plate rolling mill of one of the Italian metallurgical enterprises are considered the necessity to expand the assortment of new sizes of hot-rolled plates steel grades with high mechanical properties and, of course, to produce high-quality products with reduced operating costs. The target parameters for the product mix of the plate rolling mill after modernization are the thickness range of 5.0–150.0 mm for steel grades up to S900MC according to EN 10149–2. This work compares the technical parameters of an actual rolling mill and two modernization options: option 1 is a two-high rolling mill with increased working roll diameters; option 2 is a four-high rolling mill. Both options consider that the weight of work rolls and backup rolls with chocks will not exceed the existing crane load capacity of 80 t. When comparing option 1 and option 2, option 2 is preferable because it enables the production of low-thickness products of reference steel grade S900MC with fewer passes and assures more engineering strain. Option 2 for the rolling mill parameters provides more yearly capacity with lower electricity consumption. The efficiency of using a rolling mill with option 2 parameters is 37.8% higher than option 1 and 62.1% higher than the available rolling mill. As a result of the comparison calculation, it is obvious that a more efficient layout conception is one with four high rolling mill parameters of Option 2.