browsing rooms is deliberately not implemented in Element X yet; it's intended more as an imessage/whatsapp style messenger - plus exposing the matrix.org room directory make appstore review & age-rating etc much more complicated.
FOSDEM is upon us, and finding the right room to follow the chat is going to be much harder with Element X. Ditto for LPC which just ended. It's OK, Element for Android is still here, but I hope you'll have a solution for small servers with a controlled number of room — but that would still need browsing on mobile.
