Unfortunately there is limited chance that enough light could make it through the crystaline roof even in perfect conditions to allow for plant growth. part of this is indeed the type of material the roof is made off, but also the rotation of the earth, and a few other minor factors.
Light, Mirrors and Crystals
Although there are many materials that are translucent enough to allow light through, as L.Dutch explained these need to be polished to allow that to happen. even if you had the walls of the cave covered with nice reflective surfaces made of Gold or Silver, each metre that was reflective means that same metre cannot have life growing on it. and again each of those metres that do have life means less and less life is growing as there is less light bouncing around.
As WillK suggested, Ice is a potential option and doesn't need to be polished. however... this still has the same issue with any surface allowing reflection means a surface not housing life, and even then, as far as i'm aware, a wall of ice (insert random game of thrones reference) is not really suitable base for growing life.
Even in optimal conditions light would only reach half way down a one kilometre ravine for less than a hour a day. That's not a lot of time for plants to absorb sunlight for photosynthesis, then consider a lot less light is making its way through the roof material, and on a cloudy day that is diminished even more, and each surface the light bounces off diminishes it even further etc, so plant life would really really struggle to photosynthesize...
Ignoring fish for a minute... there are plenty of examples of life at the depths of the oceans, and corals that don't need light to live. Many of these live around hydro-thermal vents, and they get their energy needs from converting the abundance of nutrients and minerals around them, this process is called chemosynthesis, this happens at a bacterial level and then other plants and corals live off those bacteria.
Its very plausible that given the right geothermal conditions that life would exist in these caves in pools of water... perhaps those pools come from the melted glacial ice that forms the roof
Mix this with Fungi that don't photosynthesize but live off their environment, which could include living off the chemosynthesizing life... and you have most of a proper life cycle right there.
Then of course there is the very theorectical Thermosynthesis, although this has never been seen before in real life.