I'm just starting playing with the assembler and I've found sjasm and sjasmplus very good ones. They have very good support for all kind of macros and even sjasmplus support the use of LUA (I need to investigate this). Also I have used asMSX and it's very easy to use, but I think that it's a bit limited for medium or big projects,so I would like to use sjasm.
My problem is that I don't know how to generate a ROM from this assembler. I suppose that probably the code will need some header (like the header needed to run the output from basic) and perhaps it's possible to create a ROM directly, but I need more info. Is out there any tool that generates a ROM from a .com? Any idea about how I could create a ROM?