Roma was 144.6 meters (474 ft) long overall and had a beam of 22.4 m (73 ft) and a maximum draft of 8.58 m (28.1 ft). The ship had a slightly inverted bow and a long forecastle deck that extended past the main mast. She displaced 13,772 long tons (13,993 t) at full load. Roma had a crew of 742–764 officers and enlisted men.

Her propulsion system consisted of two vertical triple-expansion steam engines, each driving a screw propeller. Steam for the engines was provided by twenty-eight coal-fired Babcock & Wilcox boilers that were vented into three funnels. The ship's propulsion system was rated at 21,968 indicated horsepower (16,382 kW) and provided a top speed of 21.39 knots (39.61 km/h; 24.62 mph) and a range of approximately 10,000 nautical miles (19,000 km; 12,000 mi) at 10 knots (19 km/h; 12 mph).

As built, the ship was armed with a main battery of two 305 mm (12 in) 40-caliber guns placed in two single gun turrets, one forward and one aft. The ship was also equipped with a secondary battery of twelve 203 mm (8 in) 45-cal. guns in six twin turrets amidships. Close-range defense against torpedo boats was provided by a battery of twenty-four 76 mm (3 in) 40-cal. guns in casemates and pivot mounts. Roma was also equipped with two 450 mm (17.7 in) torpedo tubes placed in the hull below the waterline.

Roma was protected with Krupp steel manufactured in Terni. The main belt was 250 mm (9.8 in) thick, and the deck was 38 mm (1.5 in) thick. The conning tower was protected by 254 mm (10 in) of armor plating. The main battery guns had 203 mm thick plating, and the secondary gun turrets had 152 mm (6 in) thick sides.