There are various resources for finding the pitch accent of dictionary-form words, but it seems there aren't many for finding the pitch accent of inflected forms. The best I've been able to find is OJAD, the Online Japanese Accent Dictionary. Despite the English name, the site is put together by a Japanese organization, and the UI appears to be available in multiple languages.
Looking at their entry for 帰る, we see that the plain form pitch accent is かえる【HLL】. Meanwhile, the negative ～ない form pitch accent is かえらない【LHHLL】, as broccoli forest indicated in a comment. Following from that, the pitch accent for the past-tense ～なかった form is かえらなかった【LHHLLLL】.
Meanwhile, we see that the pitch accent for almost-homophonous 変える is different: plain かえる【LHH】, negative かえない【LHHH】, negative past かえなかった【LHHLLL】.
The OJAD dataset doesn't seem to include ～たい forms.
My subjective impression is that these are similar to the ～ない forms, but I will certainly welcome any input from a native speaker. Darius Jahandarie points out that the ～たい form pitch accent for 帰る is かえりたい【LHHHL】, diverging from the negative.