Resemblance between central rosette's "towers" and small-plants' "containers".

[Mark Knowles]

In one version of the Ripley scroll (Bodleian MS Ash Roll 53), there is a structure which presents striking similarities to the central rosette. There are no jars in this one, but in many versions of the scroll, the figures atop the towers are holding flasks.
Interestingly this particular version was discussed in a 2016 talk by none other than Alexandra Marraccini.
Unfortunately, the date of this version is 1600.
Still, I think it is a relevant parallel, because the number of "towers" varies regularly  (4, 6, or 7) in different versions, so if this is the basis for the Voynich image, it could be based on an early version I don't know about.
Nice frog and nude figures too

Given my interpretation of the Central Rosette one problem I see is that the Central area is not drawn the way water is in the rest of the 9 rosette foldout. The 6 objects around the Central area I interpret as ciboria. As ciborium is essentially a chalice with a lid. A chalice is a "footed" cup normally with a "pommel" around the neck of the cup. This is particularly obvious in the far right "ciborium". What are presented in this drawing as walls in the Central Rosette I interpret them as the rim of a crown. So I interpret this as a crown surrounded by ciboria. The tiers of the Central Rosette I interpret as the tiers of the Popes tiara with the rim of a crown at the bottom of the final tier. The "pipes" I interpret as cannons. I believe the Central Rosette to represent the Pope. For a more detail explanation refer to my posts on Nick Pelling's blog.