Yep. GNU Fortran at least. Others should work as well.
As with all COBOL <-> Foreign Function Interfacing there is extra burden on the programmer to keep data types in sync, or be aware of the potentials differences. Is an integer 32 bits or 64? Are source code literals signed or unsigned. Things like that, but yep, GnuCOBOL can call functions from just about everywhere. That link to the FAQ, Chapter 5, is riddled with different approaches to FFI from GnuCOBOL.
And there my be an "official" libffi user defined function repository soon too. libffi exposes a cross platform layer that allows call frame setups very similar to the JVM JNI style, with little strings for datatype specs in a CALL.
And depending on how much work you want to be doing with COBOL/Fortran linkage, there is also a SWIG-Fortran wrapper on GitHub. SWIG can make language integration a super easy thing to do. A shared interface file and targets lots of languages, right out of the box.
Cheers,
Blue