Roitan, although being the largest moon, is still rather small.
Roitan's radius is around .23 times that of earth, and its lower density makes it have a mass of .09 times it. The lower density is the result of most of its composition being from the crust of Alakla- it was formed much like the moon of earth.
Roitan is mainly silicate, but the presence of light carbonates makes it far less dense. The little core it has is mainly aluminum, and the mantle is mainly molten silicates and aluminum.
A day on Roitan lasts the same as its year- 38.5 days. This is because it is tidally locked onto Alakla. It has a few asteroids orbiting it in turn, but these are relatively tiny, with masses reaching below .1% of Earth's.
The only life on Roitan are microscopic multicellular life and mostly bacteria. They are mainly eukaryotic, as prokaryotes have nearly gone extinct here. Multicellular life is mainly forms of tardigrades and other extremely strong organisms.