I am also a ROEBECK of SAMOAN heritage who is unsure about my family tree. My father is Fritz E Roebeck and from what he's told me, all 'Roebecks' from Samoa are connected in someway. My grandmother (dad's mum) married Thomas Roebeck who is the youngest child of Olaf Frederick Roebeck and Emmy M Paice-Roebeck. I've never come across nor heard of the name 'Razilus' in my family bloodline. Perhaps it's just a coincidence that my great-grandfather's name was also Olaf? However, in your other description about Olaf coming to Samoa etc and the name Roebeck originally being 'Roback' is exactly what I've been told. So maybe we are talking about the same Olaf? :)
To add to that, I think he did have five kids, one of them being my grandfather. From what I recall his other kids included Fritz, Niccolina, Christina & Ana?
Would be interesting to know what you know about Olaf and if it matches up with what we know :):)