In September 2003, the Roadster S was introduced at IAA 2003.

The Roadster is based on the BMW Z4 3.0. It didn’t replace any existing Alpina models as no Alpina version of the BMW Z3-series was produced.

The Roadster S uses the same engine as the B3 S. Although it is based on the Z4 3.0, this means the engine is not based on the standard N52 engine, but rather the older M52 engine. In Alpina´s version it delivers 300 bhp and 362 Nm. Please refer to the E46 B3 S section for more information about this engine.

The Roadster S uses a 6-speed ZF gearbox, which is different than the B3 S. Also, the final drive was changed from the regular Z4 3.0 – 3,23 instead of 3,07.

The suspension has been uprated with stiffer springs and modified dampers. Tires are changed from the Z4 3.0 standard runflat tires to Michelin Pilot Sport, 235/35 ZR19 at the front and 265/30 ZR19 at the rear, fitted on Alpina Dynamic wheels just like the Roadster V8. Alpina Classic wheels are available as an option. The Roadster S uses the same brake set-up as the Z4 3.0.

Inside the Roadster S is equipped with sport seats in Alpina design leather, new instruments with blue background and red needles, a hand-stitched leather steering-wheel, Alpina floor mats, Alpina door sills and a silver-plated production plaque. The exterior changes are very subtle, front and rear spoiler lips are fitted. These make the car more stable at speed while maintaining a very low CW-value. The Roadster S also has two large exhaust pipes.

For the Roadster S, Alpina claimed a 0-100 km/h time of 5,3 seconds. However Auto, Motor und Sport measured a time of 5,0 seconds. Topspeed is quoted at 265 km/h, or 270 km/h with the optional hardtop.