Why would a business hire humans when it can just hire ogres or roshava which are stronger/faster? Do humans have a hard time getting jobs?
There are many reasons to hire humans over other species. Some may be political. In Evangeline Kingdom, for example, humans have more rights than other species, so they may be the first choice for many higher-level jobs.
Another reason is bigotry. Maybe the boss just doesn't like other species and prefers to hire humans instead.
There is also logistics. Maybe the area in question simply has more humans living in it, and other species aren't available to hire in sufficient numbers. Or maybe because humans have more rights in that area, they have a better education and are therefore more qualified for the job.
Different species have their own strengths and weaknesses. Ogres, for example, boast high physical strength but they are also considered very intimidating by most other species, so they are never the first pick for customer-service type jobs. In fact, you will find that a lot of species have that intimidation factor that makes them a poor choice for any public-facing job. Ogres, trolls, minotaurs, centaurs, roshava, cecaelia, gorgons, goblins, satyrs, and even dworfs are considered "too intimidating" or "too ugly" for certain professions.
Likewise, there are species which are considered naturally "charming" or "cute". This includes humans, but also elves, fauns, gnomes, and sirenes. These species are physically weaker, but that turns out to be a boon in this case because it makes them less threatening. The public responds more positively to them by default.
TL;DR: What humans lack in strength, they make up for in charisma. In other words, if Looming Gaia were an RPG, humans would be the only commoner species with decent charisma points. This gives them a solid niche which ensures that no other species can replace them. Therefore, there will always be jobs that are best suited to humans.