The only information I can find about the RAID on that motherboard is that it is from Nvidia (a graphics card company!), and this is how it is described at the Gigabyte web site: "This NVIDIA RAID function makes the RAID even more accessible by introducing the innovative windows-based facility." So probably it is not real RAID, but requires a windows driver.
Personally, I would forget about using the motherboard RAID, and use software RAID within FreeBSD instead.
Having said that: With 4 disk drives, using RAID 0 is a pretty bad idea. Why? Because the reliability of your RAID array will be 4x worse than the reliability of any individual drive. Think about it this way: If you put a single file system on the 4 disks, then the file system will be seriously damaged (probably beyond repair) if any of the 4 drives fail. Therefore the probability or rate of file system damage will be 4x higher than the probability or rate of failure of each drive.
My suggestion is: Since you have 4 drives, a single-fault tolerant RAID setup is both reasonably reliable (not great), and gives you reasonable capacity: You get 3 drives' worth of storage space, and you can tolerate any one drive (or sector) failing. I would do this within ZFS, by setting up a storage pool that contains the 4 drives, and uses RAID-Z, which is a single-fault tolerant parity based RAID system. With ZFS you also get checksums, so errors that are not detected by the drives will be found and worked around using the redundant data.
Setting up ZFS is actually quite easy.
UPDATE: Just saw that you posted something else a moment ago: You don't actually need the capacity, but are interested performance. In that case, a better option would be a 4-disk RAID 1-0 solution. That means that every bit of data is written to two disks, so this gives you 2 disks' worth of capacity. You'll have to find some ZFS documentation to see how to set this up; the obvious way (just put all 4 disks into the same mirrored pool) will give you 4-way RAID-1, where every bit of data is written to 4 disks, which gives you lower performance, ridiculously good reliability, and only 1 disks' worth of capacity. Setting up 2+2 disk RAID 1-0 may be a two-step process in ZFS.