It comes down to how big the offspring. In the idea of horses for example you can breed shires (the second largest breed) with shetlands( the second smallest) with a shire farther and shetland mother though the danger comes the child birth to the mother.
So races like Hyur elezen miqo'te and aura (seeing it seems to be puberty when male aura shoot up where females stay small) would have no problem cross breeding. Lala's I picture have to stick to lala partners for children as the female are not much bigger then a human child so a human sized baby would be a large problem for her. And carrying the child alone could be deadly. As for roes we have yet to see Roe children to get an idea of how big they are. If there like the Aura and seem to be similar to human size them spurt up at puberty it could be possible but looking at the hip span of female roes I picture the kids to be pretty big.