You can use CloudFlare's paid level plan (pro or above) and then use our Flexible SSL option which means we'd be connecting to your back-end (like Heroku in this case) over HTTP ...meaning you would not need to have SSL enabled at Heroku.
So with Flexible SSL this is how things look --
visitor <-- HTTPS --> CloudFlare <-- HTTP --> Heroku
Discussed here also: https://support.cloudflare.com/hc/en-us/articles/200170416-What-do-the-three-SSL-options-off-Flexible-Full-mean-
so with Flexible SSL your visitors can still access your website using HTTPS, but CloudFlare would be connecting to your back-end at Heroku using HTTP.
p.s. in the future I would recommend opening a support ticket with CloudFlare directly. Our support team would be able to answer this question for you quickly. :)