RWTH Aachen is a German public technical university, and most of what applies at TU Munich applies here too: for standard programs there is no tuition, the real cost is living in Germany, and institutional scholarships are few. Doctoral funding comes mainly as paid research positions, which are employment contracts attached to projects and institutes, and that is where the majority of funded doctoral places at RWTH actually sit.
The scholarship layer that does exist is visible on this page. RWTH's AROP fellowships fund international researchers coming to Aachen for short research stays, the Deutschlandstipendium provides a monthly allowance to selected students at every German university, and DAAD runs the national channel for international students through its own application process. ERC grants and similar listings below are research funding held by faculty, not scholarships students apply for, which the provider line makes clear.
RWTH publishes current openings through its central scholarship pages and institute postings, and each card links to the office that runs the award. Because positions and DAAD rounds follow different calendars, check the deadline on the specific listing you want and confirm it on the linked page before planning your application timeline.