Sometimes, the potion can be learned by studying back at home.. but:
Aphrodisiac: Water lilly + Blue Essence + Succubus leaf + [empty] + Green Essence
capturing Roushk only happened when Othra asks you to get him.. whither you are going bad or good route for the lizards.. however, i havent tried the bad route lately.
"get" as term of them loving the MC and increasing a heart, no. for the time being you may use the love potion on the Bartender, Shopkeeper, blacksmith or Filiar to have a scene [if you know what i mean]
thanks to both for the information well let's save the love potion for later and thank you very much for the recipe of the aphrodisiac.
You can get Roushk after the first capture event in the bad route.
I had both top and nottomscenes with foliar. But I wanted use the option in Roushk... lol