/usr/lib/x86_64-linux-gnu/librostlab.so.3 is in librostlab3 1.0.20-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/librostlab.so.3.0.0
/usr/lib/x86_64-linux-gnu/librostlab.so.3.0.0