This is a not too brilliant quality pdf of a monograph on the
Roman de la Rose manuscripts held by Aberystwyth University. To be honest, they're not first division medieval books, but interesting enough if this your thing. Because of the fairly low resolution you won't be able to see the fine details of the writing or illumination, but the layouts are clear enough. The accompanying essays are decidedly academic in tone! Anyway, here you go (once again the download appears to be automatic):
The Romance of the Rose illuminated: Manuscripts at the National Library of Wales, AberystwythThere are other
Roman de la Rose resources which might be interesting to anyone with the urge to grab a quill and write á la mode français médiéval, if you'll pardon my Franglais.
The Roman de la Rose Digital Library catalogues and reproduces the vast majority of extant manuscripts, but if you really want to examine a good MS in fine detail the British Library has a
fantastic digital facsimile of the Harley 4425
Roman which I can't recommend highly enough.