I know that lots of conspiracy theorists like to make this assertion. I know that he associated in circles that included members of various fringe philosophical traditions, but was he a Rosicrucian? Probably not. At least that's the conclusion that I'm aware of the consensus of historians coming to... are you aware of a different conclusion, and if so, do you have a source for it?

That's the key problem, here, is conspiracy theory has become a source-free echo chamber of supposition and "plausible enough" sounding ideas.

Now, what I do know is that neither Rosicrucians nor Freemasons are satanists, nor are they directly related to each other (though certainly one could make the claim that they come out of the same Enlightenment-era philosophical themes which in turn were largely influenced by the late-middle-ages Catholic scholars and the ancient Greek philosophers).

My sources for this are: Grand Lodge of British Columbia & Yukon: Anti-Masonry Frequently Asked Questions: 4. Isn't Freemasonry the same as Rosicrucianism? which, in turn, cites History Of Freemasonry by Albert Mackey which is, I'll admit, a bit inside baseball, but when you're talking about the history of Freemasonry and other Fraternal organizations, the mainstream historical interest tends to have been quite low, although that's been changing for the better in the past decade or so, and we're starting to see some excellent mainstream, non-Masonic histories of fraternal organizations going back to the Enlightenment. I'm really pleased about that, because I do fear that we're too echo-chambery (even though research societies like AQC are extremely well respected for non-academic historians).