The purpose of the "Atari ROM Maker" is to convert plain ROM files (".bin", ".rom") into cartridge files (".car"). The resulting files will have the correct header and checksum. As a result, emulators will recognize them correctly, and you will not be prompted to choose the cartridge type every time. Drop one or more ROM image files or folders on the window to start the conversion. Based on the file size, the possible cartridge types are computed. You are prompted to select the correct cartridge type if there are multiple possibilities. The resulting cartridge image file is saved into the same folder as the original file but with the ".car" file extensions. No new file is created if the source file is already a valid cartridge image file. If the conversion is started for a folder, you are prompted if you want to process all sub-folders and files therein recursively.

Atari ROM Maker in Interactive GUI Mode

Unlike the interactive conversion options offered in most emulators, Atari ROM Maker can also be used as a command line tool. It can be incorporated into the build process of your Atari cartridge project. This allows for a single build process that creates multiple target formats. For example, you can create ".car" files for Atarimax Maxflash, SIC!, MegaCart, and others with the same script.

Atari ROM Maker in Command Line Mode

Atari ROM Maker is open source, written in pure Java, and runs fine on Windows, Linux, and Mac OS X.
The download is available here. The sources are available here.
The definition of the numeric ids for the different cartridge types is available as part of the Atari800 project here.
Feedback is welcome and can be posted in the AtariAge (English) threads and the ABBUC forum (German).