There can be such a thing as a deep, deep love between people (and not always sexual although intimate) that could be cast as romantic or not but it is something I think Frodo/Sam share - that they are essentially soulmates and that while not sexual at all in the books and even though there ar intimate moments, it is something deep and true. Something that not even Rosie will get from Sam.
If anyone has read the epilogue Tolkien wrote for LotR (but wasn't published with it) it is very obvious that Sam is still torn in two despite Frodo's "sacrifice" and while very pleased with is life and his wife, still longs greatly for the sea and to see Frodo again.
I know that many just want it to be a "friendship" and not "gay" but then I think that it is a dishonor to their relationship to simplify it to that kind of argument. It is obviously love, it is obviously friendship but it is also so much more.