I wanted to use gravity assist to hurl some of the rocks and dust in the planetary ring in quick succession onto the enemy's direction, what kind of future technology am I looking for? Is there a way to aim in any direction and how to reload?
Huge, enormous lasers. https://what-if.xkcd.com/13/
Mega-powerful lasers on your planet's surface can aim at the retrograde side of debris in the planetary ring, evaporating some of it at high temperatures. As the material ablates away and spews off into space, the equal and opposite reaction will thrust the remaining solid bits in the prograde direction. This will boost the debris into a more eccentric orbit that might hit your enemy. With strong enough lasers and large enough debris chunks, you could maybe get escape velocity.
What you'll need is huge banks of impossibly powerful lasers that can target and incinerate things in orbit with pinpoint accuracy.