You don't seem to understand the first amendment. The boss is denying the person's right to freedom of religion by not allowing him to do one of the required daily activities of the religion. The boss should be in trouble.
We just had a discussion about this today in class during a "prayer in school" debate.
Are you willing to accept that the results of such a debate may not be accurate?
I don't really care about the constitution of the united states of america. To be fair, it isn't an anarchist state with corporate building that are armoured bunkers that settle disputes with artillery barrages, with schools that are concentration re-education camps, probably, hopefully... And the its constitution may have contributed to this somewhat. But there are certainly arguments that it is severely flawed...
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof.
Assuming that this is accurate, and sufficiently comprehensive for the argument. It quite specifically says that it applies to congress, which quite specifically says that it does not apply to anything else. Regardless of the context, unless something ridiculous, like the sentence starting with "Everything including Congress" or something similar, this statement has no bearing on what an employer demands of an employee.
It does, however, require congress to avoid creating laws that prevent practising a religion, which really has to be taken lightly, as ANYTHING can be adopted as a religion, and usually has...
In the employer/employee example however, the relevant laws suggest that services can be expected once paid for, so no more capitalism... In this example the employee never should have agreed to a contract that wasn't compatible with their religion. This is a religious tenet as well as a legal one. So what do you do? Give religious freedom authority over legal contracts? Then you just need to find a religion that would disqualify a contract and you could abandon it. Do you know how many religious practices there are? Or you could force contracts not to include anything that might impede a religious practise. So they can't mention times when an employee is expected to work. They need to provide access to religious facilities and staff, even for people who work in space stations, so they need to be willing to send up shrines, ministers, swords... Oh yeah, the sword thing, it is a real religious requirement, they need to allow people to carry swords, school teachers, airline staff, even when they are walking through the aisles, prison guards, prisoners, psychiatrists, orderlies... What about soldiers, lets say that someone feels that their religion forbids them from, say, killing people, you can't deny them employment due to their religion, you can't force them to act against their religion, so you need to allow fighter pilots, tank gunners, front line infantry, snipers, and whatever else who are not allowed to kill people...
And what about the religion that demands unwilling human sacrifices? Oh, so only within reason... Where exactly does unwilling minors being withheld blood transfusions fit in?