You will not find a "complete" 1GB Fantom-X library for free. That would require pirating Roland’s copyrighted waveforms. The free SoundFonts are derivative works—samples played by users, not the original ROM dump.
Since these are often user-sampled, look for "multisampled" versions to avoid "chipmunking" (distortion when playing notes far from the original sample pitch). Legacy Hardware: roland fantom x soundfont free
from enthusiast groups to add modern rhythmic sequences to his mix. You will not find a "complete" 1GB Fantom-X library for free
Before you download, you need to understand the landscape. you need to understand the landscape.