This very common word has joined the concordance in honor of its unusual use in the apple-barrel song of Chapter 9:

[09.049] Roll – roll – roll – roll,

roll-roll-rolling down the hole!

In the top line, the words “roll” are separated by spaces and hyphens, a repetitive phrase; but my goodness!  roll-roll-rolling has no spaces!  It is one word, and the OED assures us that the reduplicative is “a word form created by reduplication”.  I think that such a reduplicative even qualifies “roll-roll-rolling” as a vocable and sound play.

• 01.066 Send them down the hall to roll!
• 01.066 Send them down the hall to roll!
• 02.070  and rolling nearly into the fire
• 04.004  and go rolling
• 04.036  and rolling
• 04.043  – for dwarves can roll along at a tremendous pace,
• 04.051  and the hobbit rolled off his shoulders into the blackness,
• 06.040  rolled away from their feet;
• 06.040  and rolling;
• 06.065  and unless they rolled over quick they were soon all
• 06.065  Very soon all about the glade wolves were rolling over
• 07.035  He laughed a great rolling laugh,
• 07.093  in rolling round drum-shaped sections of logs,
• 07.094  Beorn in his deep rolling voice told tales
• 07.099 and like a tide it roared and rolled;
• 07.108  and had rolled down with a bump from the platform on to the floor.
• 08.104  and rolled off the branch dead.
• 08.108  that he just rolled off the branch
• 09.048  they answered rolling the barrels to the opening.
• 09.049  Roll – roll – roll – roll,
• 09.049 roll-roll-rolling down the hole!
• 09.054  was being rolled to the doors!
• 09.055  the barrel rolled round
• 09.059  roll off again
• 09.060  a round-bellied pony that was always thinking of rolling on the grass.
• 10.034  and it rolled loud
• 12.076  The dragon rolled over.
• 13.008  and rolled headlong into the hall!
• 14.033  in the roll of the benefactors of our town;
• 16.047  in turn rolled himself up
• 17.040  Winter thunder on a wild wind rolled roaring up
• 17.046  rolling away to the South-East;

“reduplicative, n. and adj.” OED Online. Oxford University Press, June 2017. Web. 5 September 2017.