Thread: Minor Problem

Code:

void main()

Nonstandard. Read FAQ!

Code:

scanf( "%s", romanchar );

Unsafe! Read scanf format specifiers better or consider using fgets.

Code:

counter = 0;

Not necessary since you're initializing it to 0 in the loop anyway (though the compiler will probably remove it when compiling a release anyway).

Code:

sum = sum + 4;

All these can be written as sum += (number);

Code:

sum = sum + 1;

Can be written as sum++.

Consider using proper indentation as well.
But code in itself, however, is not faulty. It compiles fine.