I believe it this what it corresponds to. It's often spelt as one word: rouletabosse.

"Roule-ta-bosse, rouletabosse, subst. masc. [...] Cylindre d'une machine à carder la laine, destiné à la débarrasser des chardons."
http://www.cnrtl.fr/definition/roule-ta-bosse

It's a cylinder or roller in a carding machine before the main cylinders, whose function is to open up the tuft and remove excess vegetable matter ("débarrasser des chardons").

"1è Fonction - Diviser la nappe de laine, alimentée et étalée en épaisseur régulière sur la toile sans fin F, en mèches, à compte de libres aussi réduit que possible.
Cette fonction est fournie par les cylindres alimentaires A et le rouletabosse B."
http://tricofolk.free.fr/Filage/cardeuse_industrielle.pdf (p. 8)

This quotation is from chapter XV of « Transformation des laines brutes en fils peignés » (1913). The "rouletabasse" is marked R in Figure 62 on p. 9. The cylindres alimentaries (A, A') are the feed rollers (or feedrolls).

"R, Rouletabosse, garni en dents de scie, inclinées suivant le sens de rotation. Organe divisant, en mèches, la nappe de fibres alimentée et maintenue par A,A'."

Now compare that with this, and particularly compare the image here with Fig. 62 in the source just cited:

"Basic Function of Licker-in:
- To open the cotton into very small tufts.
- To extract the seed bits, sand and other vegetable trash particles from cotton.
- To transfer the cotton into the cylinder surface and distribute the fibres as evenly as possible both transversely and longitudinally on the cylinder surface.
- The roller that receives fiber from the feedroll(s) is called the licker-in.
- The licker-in rotates upward as it takes fiber away from the feedrolls."
http://dktetextilenotes.blogspot.com.es/2014/05/an-overview-...

It's also called the "taker-in" here, but I like "licker-in" and I think it's more standard.

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Note added at 1 hr (2015-11-08 11:31:42 GMT)
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I do hope you can open these pages and see the pictures, which are a great help. I think you can match them up with this other description:

"On utilise généralement une carde à deux tambours, dite « carde double », précédée d’un avant-train et d’un cylindre briseur appelé rouletabosse, le tout étant complété par un ou plusieurs dispositifs échardonneurs intercalés sur le parcours suivi par la laine. La zone où s’effectue le travail de cardage est constituée de plusieurs cylindres de diamètre de cinq à huit fois plus faible que celui du tambour qu’ils entourent. Ces cylindres portent le nom de travailleurs ou de hérissons."
http://www.larousse.fr/archives/grande-encyclopedie/page/540...

The "avant-train" corresponds to the cylindres alimentaries/feedrolls. The "rouletabosse" or licker-in is the cylinder labelled R in Transformation des laines brutes (which is by Léon Faux, by the way), and you can see the "dispositif échardonneur" in Faux's Figure 62, labelled (e):

"e, Echardonneur à ailettes rayonnantes évitant, en plus de son action d'extraction des chardons, l'entrée de corps solides étrangers susceptibles de détériorer les garnitures de la carde. Les chardons et les corps étrangers sont projetés dans le récipient b."

Then the main drum and the smaller "travailleurs" or "hérissons" come straight after the "rouletabosse" and are labelled T and T1-T4 in Faux's Figure 62.

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Note added at 1 hr (2015-11-08 11:47:13 GMT)
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Another EN source, the Wikipedia article on carding, which is basically about wool:

"Drum carders
The simplest machine carder is the drum carder. Most drum carders are hand-cranked but some are powered by electric motor. These machines generally have two rollers, or drums, covered with card clothing. The licker-in, or smaller roller meters fiber from the infeed tray onto the larger storage drum. The two rollers are connected to each other by a belt- or chain-drive so that the their relative speeds cause the storage drum to gently pull fibers from the licker-in."
https://en.wikipedia.org/wiki/Carding

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Note added at 1 day6 hrs (2015-11-09 16:43:23 GMT) Post-grading
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Thanks to you! Probing a little further, I think you're right about "pre-roller", which seems to be preceded by "preliminary rollers" sometimes. All rather technical. But I think it's worth adding "pre-roller" to the glossary entry for future users.