A friend picked this up during a trip to Germany. I looked online for information on Rokomatic but all I found were some eBay ads, also in Germany.
In spite of the name, all the Rokomatics seem to be hand-winders. The brass waterproof case is interesting in that it is unplated. It's 34mm in diameter, 41mm across the lugs, 10mm high, and the lug width is 18mm. There is no country of origin indicated anywhere but the strap is marked Echt Leder, so the strap is probably German. It's possible that the strap is original since I saw a photo of another Rokomatic with the same strap.
The only markings I can see on the movement are CAT-C 66 and 17 JEWELS. The bridge plates appear to be simple metal stampings, not a high-end movement at all. There's a button to press that releases the stem, a nice detail.
I am guessing it is German and based on the red second hand, from the 50s at the earliest.