Former Reds captain Henderson is enjoying a late career revival with the Bees this season.
"I think if I even tried I don't think he would text me so I'll save that for after the game," said Robertson.
"He's an absolute legend of our club, what he has done for us within our changing room and the trophies he lifted and guided and led us to trophies.
"He's an absolute legend for all of us who were lucky enough to play with him, he's a legend to the fans and everyone connected with the club. It will be nice to see him but I know he will be up for the fight like he always is.
"Our midfield will have a hell of a battle against him, like all our players will because Brentford are a tough team. Hopefully if we get the win I can have a nice catch-up with him after the game!"
Robertson also said: "When you are on a losing streak it is important to end it as quickly as you can. The message from the leaders in the group after Manchester United was, 'Don't panic'.
"We need to get our performance levels lifted and that's a fact and that's what we tried to focus on, lifting our performance levels with and without the ball. We knew if we did that then the result should be on our side. Thankfully we did that.
"When we go 3-1 up you see lads starting to enjoy themselves and that's what you want, people playing with a smile on their face and people enjoying playing for this club, people scoring goals, people assisting goals.
"Winning 5-1 in the Champions League is quite rare."