from where did you get the information that roasting rue will turn harmine into harmaline?
Also, what tribe are you talking about that does the cold extraction? Because you are adding lemon to it, which makes a big difference. In brazil when they do this they dont add acid. Jace Callaway's research showed that yuremamine, the alkaloid that might be responsible for cold jurema's oral activation, is destroyed with acids.. They dont take with MAOI containing plants (except sometimes smaller amounts of passionflower but that has minimal if any MAOI so it doesnt really count), so the fact that there's no acid added is essential. Also if you look at ott's publications, he tested and said that for cold water extraction of mimosa, the dosage is around 25g.
I would suggest forget that roasting (also because even if harmine would turn into harmaline, which I would like to see some source for the claim, many people find harmaline to be more sedating and not so pleasant, so better keep harmine).
Another 'mistake' I think you did was just making one soak for everything. Its a fact that one single soak wont get all the alkaloids, you'll be losing a lot (just like one soak with your clothes wont wash them so well, better 3 or so).
I would suggest next time you do 3-5g mimosa and 3-4g rue, boil 3x. Check the FAQ for more information on how to brew. If you still want to go for the cold water extraction (CWE), do maybe 2 soaks and add no acid and try more like 20g mimosa instead, with no rue. I never tried CWE so I cant say from experience, but the boiling 3x mimosa+rue (separately or together) I can guarantee it will work if your mimosa or rue arent bunk