Gandalf on Tom Bombadil

[Mumriken]

Just saw this quote on the top of this site and it had me thinking.

He is a moss-gatherer, and I have been a stone doomed to rolling. But my rolling days are ending, and now we shall have much to say to one another.

So Gandalf is a rolling stone and Tom is a stone with tons of moss on it. Hmmm there are several ways to interpret this. First a stone must be pushed to start rolling, so the valas pushed Gandalf down the hill. Bombadil is a moss gatherer, the big question is what is the moss? Does it just mean he hasn't been rolling or could it mean anything else? Also why isn't Bombadil rolling? Could the valas not make him roll?

Are there any benefits to being a rolling stone and a stone gathering moss. Is there a possability that Tolkien by using this analogy gives us hints as to what Bombadil are or how he stand in relation to Gandalf?

I'm looking forward to see how you interpret the moss and the rolling stone analogy thing.

(What is the moss)
(Differences between rolling/mossy stone)
(Why isn't Tom rolling)