While this comment is well intentioned, you do not own the ROMs. Using the example of the SEGA Mega Drive and Genesis Classics [0] Steam listing the EULA states:
> THIS SOFTWARE IS LICENSED, NOT SOLD.
> 3. NO RIGHT TO OWNERSHIP
YOU ACKNOWLEDGE AND AGREE THAT YOU SHALL HAVE NO OWNERSHIP
If you look at the Steam store page there are numerous reviews from people who bought the collection only to have Sega remove some of the ROMs from the collection making it impossible to play these games that you paid for.
> THIS SOFTWARE IS LICENSED, NOT SOLD.
> 3. NO RIGHT TO OWNERSHIP YOU ACKNOWLEDGE AND AGREE THAT YOU SHALL HAVE NO OWNERSHIP
If you look at the Steam store page there are numerous reviews from people who bought the collection only to have Sega remove some of the ROMs from the collection making it impossible to play these games that you paid for.
[0] https://store.steampowered.com/app/34270/SEGA_Mega_Drive_and...