We had the chance to dig into a Roth Steyr 1907 selfloading pistol recently, and put together a video on it. The pistol is quite unusual, with a fixed internal magazine, rotating barrel locking system, and quasi-double action trigger mechanism (actually quite similar to modern striker-fire pistol trigger mechanisms). Have a look:
The successor to the 1907 was the Steyr 1912 (aka Steyr-Hahn), which shares its rotating barrel system, but uses a conventional hammer-fired trigger mechanism. Other rotating-barrel pistols have been tried, but none of them have been particularly successful.