The 18-year-old was handed a starting role alongside stand-in captain Olivier Ntcham in defensive midfield, and acquitted himself well despite the hosts running out 2-0 winners on the night.
Revealing he had been shocked to learn of his place in the starting line-up, Robertson felt he gave a good account of himself.
"I was taken aback on Wednesday when I knew I was starting. I was a wee bit nervous, but mostly it was excitement during the day."
Describing his debut as a "dream come true for me and my family", Robertson added: "I thought I played okay. I started the game quite well.
"It took a while for my second wind to kick in but I thought I grew into the game very well."
Lennon added: "Scott made his debut and was terrific. For such a young player he showed such maturity and composure."