'Let's roll' has subsequently - and inevitably - become the object of a trademark
dispute (along the lines of the longer, trademarked phrase 'Let's Get Ready to Rumble
'). The 'Todd M. Beamer Foundation' - a non-profit organisation endorsed, but neither set up nor run, by Lisa Beamer
, one which does not yet seem to have actually achieved anything - currently has the strongest legal case for using it, although over a dozen other entities
have filed trademark claims for the phrase (a similar case involved a man called Michael Heiden
who tried to trademark 'World Trade Center' during the afternoon of September 11th, reasoning that if Disney could trademark the words 'Pearl Harbour', what was stopping him from staking his own claim to history?).
The most obvious application for such a trademark would be either to make money from sales of branded products, such as mugs and t-shirts, or to imbue the speaker with a certain moral gravitas, just as the triumphant chords of Bruce Springsteen's 'Born in the USA' became a universal political jingle in the mid-80s. Many companies and individuals who are unconcerned with legal niceties are and have been doing just that ever since, most famously George Bush and his Republican hordes, who have been trotting it out ever since (most recently during their victory in the Congressional elections).
The legal disputes and delays have at least achieved one positive result result for the Todd Beamer Foundation; without them, it's likely that 'let's roll' will become divorced from Beamer entirely, with diastrous consequences for the Foundation, given that their major asset is these two words in this specific order.