I've just written a long post http://www.reddit.com/r/badhistory/comments/285382/june_moratorium_thread_14_june_2014_rommel_being/ci7sswf to explain this guy. Short answer: likely yes

• There is this new evidence that the Brits knew through bugging the POWs' room that Rommel ^[finally did support the assassination attempt anyway]. I do think that he only did this with great reluctance though, as I've explained ^[here]. Knowing there are still a lot classified military documents on Rommel and others, it seems Churchill did in fact know a lot about Rommel, much more than us currently, when he said this:

He also deserves our respect because, although a loyal German soldier, he came to hate Hitler and all his works, and took part in the conspiracy to rescue Germany by displacing the maniac and tyrant. For this, he paid the forfeit of his life. In the sombre wars of modern democracy, chivalry finds no place ... Still, I do not regret or retract the tribute I paid to Rommel, unfashionable though it was judged.

• More importantly, there are many sources that prove he was plotting an armistice in The West (with or without Hitler's approval) before the Allies strafed his car. Whether he helped in the assassination attempt or not, he did enough to "deserve" the death sentence Hitler reserved for him, like say: writing an ultimatum to Hitler^[link1]^[link2]^[link3], polling his subordinates asking them whether they would support him against Berlin's order - and apparently even the SS generals who had plenty reasons to doubt and hate him for his history of animosity towards them^[1]^[2] chose to follow him^[link4]^[link5], or trying to drag his colleagues and superiors into the plot^[link6] ^[link7]^[link7]^[link8]

Allow me to add that on top of the sources quoted by Treebeard, we have indirect accounts of how Rommel's stance toward the German resistance developed: There's a secretly recorded account by then-captured General Heinrich Eberbach as well as the post-war accounts by Lieutenant Generals Alfred Gause and Hans Speidel, who both knew Rommel well - indeed Speidel was himself part of the plot and the one to initiate the contact between the plotters and Rommel. Yet another account comes from Hans Bernd Gisevius, an early member of the German resistance who managed to hide after the plot and then flee to Switzerland.

From those accounts it seems that at least initially, Rommel disapproved of the July Plotters' plan to assassinate Hitler which he saw as backstabbing murder that he feared would also martyr Hitler; instead Rommel preferred to arrest and try Hitler in court. However later in 1944, after having openly clashed with Hitler at meeting at the latter's Berghof (June 29th) and after having met with members of the conspiracy like Lieutenant Colonel Caesar von Hofacker (July 9th) etc. Rommel seems to have finally agreed to lend his support to the conspiracy.