Do the rooms have both 220 and 110 to use for phones, tablets, etc?
to the best of my memory, no.
Shaver sockets (two round pins) in the bathroom are both 230 and 110 volts but at 50HZ.
Charging your phone or laptop can be done from the normal 230 volt sockets with an adaptor from American to European converter. Laptops and phone chargers allow for a multi voltage/multi frequency input and give the same DC output voltage for charging.
I used a converter.
Our room had both 220 & 110
I don't believe they have both outlets. However you don't need the 110 outlet for charging your phones and tablets. However you will need the pin converter from the Czech to the US.
Get an answer from Sheraton Prague Charles Square Hotel staff and past guests.