Haven't Martin been using it in guitars forever? I think they would know a thing or two about it but here is what i found off a guitar wiki regarding tonewoods, this is about tonewoods in guitars of course so while a uke should be pretty similar there make be some variation due to the relative size difference...
Back and Sides
Besides serving to form the enclosure of the soundbox, the back and sides of the guitar also act as a sympathetic resonator whose oscillations contribute greatly to the harmonic mix. When judiciously selected (with due consideration given to design criteria and the other tonewoods used in the instrument), the back and sides can have a tremendous effect on the overall tone of the instrument.
Brazilian and Indian rosewood have an extremely high velocity of sound and a broad range of overtones. The rosewoods, as well as their various rain forest cousins-cocobolo, kingwood, morado, and the like-have strongly pronounced low overtones, usually the lowest resonating frequencies in the entire guitar. These lows help to create a complex bottom end and to impart an overall darkness of tone to the instrument. Strong mids and highs serve to reinforce overtones generated by the top, contributing to a fatness of tone on the upper registers. Guitars made of rosewood also have a pronounced "reverby" tone, caused by a strong, clear set of sympathetic harmonics with a delayed onset and slow decay.
I’ve found that Brazilian rosewood has everything that Indian rosewood has, only more. I say this with great trepidation in light of that species’ likelihood of extinction within a couple of generations. An international embargo on trade on Brazilian rosewood products guarantees that the relatively few sets remaining in this country, which may be used only on domestically sold guitars, will continue to spiral in price as the supply dwindles.
Mahogany and koa have relatively high velocities of sound when considered as materials for backs and sides and thus contribute much to overtone coloration. Lacking the low-end frequencies of the rosewoods and also their sustaining reverberation, these woods have an altogether different sound. Where rosewood guitars can be thought of as having a "metallic" sound, mahogany and koa guitars are better described as sounding "woody, although the harder, more dense examples of these woods can take on some of the characteristics of the rosewoods. Between the two, koa seems to have a little more fullness in the midrange, while mahogany tends to favor the bass (to some extent) and the treble.
Maple and walnut tend to be more acoustically transparent than other tonewoods, due to a low velocity of sound and a high degree of internal damping. That is to say that they allow tonal characteristics of the top to be heard without the addition of extraneous coloration and may even serve to attenuate some of the overtones emanating from the top.
The harder, denser examples of these woods, such as sugar maple and black walnut- particularly quartersawn examples-tend to lean slightly more toward the tonal direction of mahogany, while softer examples, such as bigleaf maple and claro walnut, tend toward greater tonal transparency. Curly, quilted, or bird’s-eye figures do not seem to have much effect on the tone of the wood, but they can be used, like bearclaw, as an indicator of other properties. Quilted figure, for example, occurs most often in softer species and is best displayed when the wood is flat sawn-two characteristics that tend to produce higher damping properties.
Incidentally, you mention that the uke you are looking at is a laminate and as such the facing wood doesn't have really much to do with the tone, with a laminate it's the build quality and thickness of the laminate that makes most of the sound.
What are the qualities of Rosewood as a tonewood? I'm looking at a Moku Ukulele that has a Rosewood laminate side and back. I've rarely seen it used on the body of a uke. Can anyone tell me why they would use it other than beauty?