And powerhouse centre Roberts believes the key to victory is to apply unbearable pressure on the World Cup winning No10 at the Stade Velodrome.
"Jonny is obviously very talented and at the helm of everything they do," said Roberts, who played in the first two Lions Tests last summer before injury ended his superb tour.
"He is a very authoritative player and everyone is aware of what Jonny brings to the game.
"He controls the game fantastically, his kicking game and variation is world class and is a big threat with ball in hand. He is a match-winner for Toulon so we will respect him.
"But pressure is the key. Our defence will have to be on the money and pressurise him.
"Discipline will be huge because if we give away penalties in their half, Jonny will pin us in our 22 and anything in our half he will knock over the three points.
"But we have done our homework this week and hopefully we will be very effective in combating everything Toulon throw at us."
The Blues travel to the south of France full of confidence following seven straight wins, with Magners League triumphs over Ulster (twice), the Scarlets, the Dragons and Munster, and knock-out European successes on the road at Newcastle Falcons and London Wasps.
And HSBC Player of the 2009 Lions Tour Roberts has dismissed the notion Dai Young's men will be underdogs against the French giants.
"It's been mentioned that we are underdogs but I don't think that's the case at all," added Roberts.
"We have huge talent in our squad, we're full of confidence and playing away from home isn't a big factor for us.
"Of course, Toulon are a very attack-minded team with great individuals and a team that would cut most sides in world rugby apart in a second.
"They are a tough team to defend against and if you sit back against these French sides and let them play then almost 100 per cent goes against you.
"They will cut us to shreds so we have to apply pressure in defence and make them panic and hold on to the ball when we've got it."
The Blues aim to make history by going one better than their only previous European final appearance - the extra-time defeat to Toulouse in 1996 as Cardiff RFC.
And the Welsh capital side also want to banish the painful memories of losing the Heineken Cup semi-final on penalties to Leicester Tigers last year, a defeat that meant they missed out on a Murrayfield showdown with Leicester Tigers.
"That was hugely frustrating but this is a great opportunity to make amends for what happened last season.
"It's a huge match for the club and it should be a great advert for European rugby because both teams play attacking rugby."