The invention relates to a guide roller comprising a bearing journal (13) at each of two ends. Each bearing journal is provided with a plain bearing (14), which is designed as a hollow journal, and can be connected to the coolant supply line in order to conduct a coolant through the hollow journal into the coolant channel (12) or to conduct the coolant out of the coolant channel. The plain bearing (14) is lubricated by the coolant that is conducted through the bearing journal (13) designed as a hollow journal. A roller assembly for a strand casting system is provided with a plurality of said guide rollers (1). The guide rollers are arranged at an axial distance from each other along a strand (2) produced by the strand casting system and are each rotatably supported in a respective bearing mount (3). Each bearing mount is arranged on at least one frame part (4, 5) in a preloaded manner. The bearing mounts (3) are supported on the frame parts (4, 5) so as to be self-setting by means of elastically pliable connecting means (6). Even if the strand cross-section of the produced strand changes during the operating duration or due to changed process parameters, the originally set pressing force of the guide rollers remains substantially unchanged.