There are a supermarket and a baker's in Rathen.

The baker's is openend from April to November 
Opening hours:
Monday - Saturday from 7:30 am to 6:00 pm
Sundays and public holdidays from 10:00 am to 6:00 pm

The small supermarket provides a basic product range for your everyday shopping list.
Opening hours:
Monday to Friday from 8:00 am to 11:00 am and from 2:00 pm to 5:00 pm
On Saturdays the shop is only open in the mornings (from 8:00 am to 11:00 am)

EDEKA in Königstein (Dresdner Straße 6B) has a wider range of products.
This supermarket is only 750 meter from the railway station and can be easily reached by public transport.
Park your car in Rathen and EDEKA is still the obvious choice.
Opening hours: Monday to Friday from 8:00 am to 8:00 pm and to 6:00 pm on Saturdays.

Kaufland in Pirna (Lohmener Straße 12c) offers a broad range of relatively good quality products.
Opening hours: Monday to Saturday from 7:00 am to 10:00 pm. At a distance of 17,5 kilometers and 25 minutes travelling time approximately.

Other options are the PENNY-Markt and the Lidl near the bridge over river Elbe in Bad Schandau.