The common roach can be distinguished from similar species by the placement of the backfin and by the number of scales between the tip of the ventral scales and the first ray of the anal fin. The common rudd, for example, has only one or two scales, while the roach has four or five scales there. It is bluish silver in colour, becoming creamy white at the belly. The roach has a rather streamlined, oval shape. It has 40 to 45 scales along the lateral line, and its scales are moderate sized and firmly attached. All the fins are tinged red, except the dorsal and tail fins. The roach is often recognised by the large red spot on the iris above the pupil. With a lifespan of up to 20 years, it can grow up to 35 centimetres in length and can weigh up to 1.3 kilograms.
Found in rivers, ponds and other water bodies, the roach prefers warm, moderately flowing, vegetated waters.
The roach is a shoaling species and an omnivore. Adult species feed on invertebrates, larvae, molluscs and filamentous algae. Large specimens may also feed on their young, if abundant. The roach spawns in spring at a temperature above 8 degrees Celsius. The eggs are attached to vegetation, which protects the larval and young fish.