The Englishman was down 4-0 in his qualifying clash with China's Zhao Jianbo, yet he refused to throw the towel in and fought back to take an astounding 5-4 victory.
Robertson is a former European Masters champion, having claimed the title back in 2018 with a 9-6 win over Joe Perry in Lommel, Belgium.
His chances of a 2022 appearance looked slim when Zhao reeled off four straight frames with impressive breaks of 82, 53, 63 and 69.
The 18-year-old had a plethora of opportunities to seal victory, but failed to close out the show and paid a heavy price as Robertson began fighting back.
The 36-year-old from Bexhill-on-Sea took the next four frames with top runs of 65 and 51, before edging his opponent in a decider which lasted a gruelling 43 minutes.
Robertson will now take on Andy Hicks in the opening round in Furth, Germany.
Elsewhere, Zhang Anda produced the first 147 break of his career as he cruised to a 5-1 victory over Anton Kazakov.
After losing the first frame, the world number 87 hit back with a maximum before going on to secure his first-round spot.
Hossein Vafei also joined the 147 club after producing his first official maximum in a 5-1 win against Ng On Yee.
Former world champion Stuart Bingham sealed his progression with a comeback victory over Michael Holt. The 46-year-old went from 3-2 down to secure a 5-3 win.
Amateur Daniel Wells top scored with 85 to beat veteran Peter Lines 5-3, while James Cahill dazzled with runs of 75, 94, 55 and 90 in a 5-1 demolition of Adam Duffy.
Marco Fu, meanwhile, scored his first win in a ranking event since 2020 after beating David Gilbert 5-1. UK Champion Zhao Xintong also progressed with a 5-2 success over Fraser Patrick.