You have various approaches:
1) copytruncate in the logrotate script, this will work reliably and without the help of uWSGI
2) uWSGI log rotation: --log-maxsize <bytes>
will automatically rotate logs when a specific size is reached
3) classic logrotation + log reloading, just add --log-master
and trigger log reloading with http://uwsgi-docs.readthedocs.org/en/latest/MasterFIFO.html
There are other approaches too (like triggering the log reopen when touching a files), but the previous one are the most common.