Heating and/or temperature-maintaining furnace (11) for slabs (35), which includes lateral intake (12a) and outlet (12b) roller conveyors the axis of which is at a right angle to the axis of movement of the slabs (35) within the furnace (11), the roller conveyors (12a-12b) consisting of a plurality of roller-bearing bogies (13) able to move at a right angle to the axis of the roller conveyors (12a-12b), the roller-bearing bogies (13) having a first maintenance/replacement position (13a) outside the furnace (11) and a second working position (13b) in which they cooperate with the inside of the furnace (11), means being also included for the movement of the slabs (35) in the furnace (11), the rollers (10) being supported at both their ends on the roller-bearing bogies (13) by supporting means (19) and being driven by appropriate motor means (21), the supporting means (19) and motor means (21) being located outside the furnace (11) when the roller-bearing bogies (13) is brought to its second working position (13b), the ends of the rollers (10) being accessible from outside the furnace (11), an insulated bottom (39) and insulated sidewalls (22) being included in the roller-bearing bogies (13) to protect the roller-supporting means (19) and the motor means (21) associated with the rollers (10).