If you're open to a paper dictionary, the Dehgani learner's dictionary (https://smile.amazon.com/Persian-Englis ... dictionary
) includes transliteration (like most Persian-English dictionaries). A feature I found particularly useful in this one is that when there are multiple Persian translations for an English word, it labels the most common form.
There are predictable vowel patterns for Arabic loanwords in Persian; if you master those patterns it will make vocabulary development a lot easier. You'll probably need/want to learn them at some point anyway.
A good source for audio pronunciation guidance is forvo.com, which should have a lot of Persian words. I don't think it provides transliteration, though.
The online Hayyim dictionary at the University of Chicago (https://dsalsrv04.uchicago.edu/dictionaries/hayyim/
) includes pronunciations, e.g. بلند (boland). It's an older dictionary but you should be fine with common words. I don't know how you are with software development and scripting, but if you had an existing frequency list in softcopy you could, in theory, run a series of queries and parse the results returned to extract the transliterations, if you wanted to do a bulk conversion. On the other hand, if you were learning these words as you looked up the pronunciations, maybe one manual lookup at a time would be fine.
Ilya Frank's Website used to have a free book of Persian fairy tales with interlinear Russian translations and transliterations into Latin characters. I don't know whether the Russian would be of use to you but reading through the original Farsi and transliteration together might help. And again - it would, in theory, be possible to write a script to generate a frequency dictionary paired with Latin transliterations from that book, since the words should line up perfectly.