You don't have an array of roll, pitch, and yaw values, do you? I thought you had one of each. Yes, they are 4 bytes, but that is the size of the float, not the number of floats.
radio.write( voodooS)
That "voodoo" is the address of the struct and the size of the struct.
radio.write((byte *)&StructBuff, sizeof(StructBuff);
Both ends need to know how that struct is defined, so the sender packs the data in it correctly, and the receiver gets the data out correctly.
Like the box and envelope analogy, the post office doesn't need to know what is in the box to deliver it. The recipient needs to, though