If you're already familiar with the text or at least have an open mind, this is a film of absolute freedom, and a profound love of the world, as you take, as his followers did. There is a lot of playfulness, Rossellini is a mature director and was neither mocking nor sentimental, he was free, like them.
Just watched the lovely restored version of Rosselini's "The Flowers of St Francis" (1950), co-scripted by Fellini. I believe it is Rosellini's own favorite work--with most of the cast being non-professional actors (actually monks!). It reminds one of Pasolini's "Gospel According to St Mathew." My favorite segment in the Rosselini film was the one with the tyrant Nicalaio and Br. Ginapro.
Beautifully shot film that presents vignettes from the life of Francis of Assisi that presents so-called Christian values of charity, sacrifice, and poverty. Mind you its also a group of men blindly following a self proclaimed vessel of God. One person's viewing could be a deeply religious experience allowing them to question the tenets of their own faith, but another's take may be the cult like aspects shown.
It was impossible for me not to wonder - what do you see if you are western and (at least culturally) Christian...? And is it not vastly different from what you would see if you were born into a foreign culture? Are those not a group of very strange men with masochistic tendencies, bizarre rituals, inexplicable acts of psychological self-immolation and above all an unnerving dedication to a nebulous master?
Rossellini's camera eye is the only I've encountered that seems perfect, by which I mean that his composition choices seem like the only ones possible for any given shot, by a logic that is as certain as that of mathematics but impossible to articulate. I can't think of another film that stands as a better rebuke to the empirical, science-inflected strain of film criticism so popular today.