Hey guys,
I´m working on an audio drama with elementary students. Since i have very limited possibilities, i did the voice recordings in a normal room. Now i have a lot of room reverb in the recordings. I tried  a demo of "Acon Digital Deverberate" on them to remove the reverb, and it works fine, but costs 100€ . So if you guys have a solution with stock/freeware plugins, i would be happy if you share it with me.

I use SPL De-Verb which works well. The new version comes with a dry and wet control. SPL Transient Designer Plus which comes with a sustain and attack control, internal sidechain and wet/dry control. Designed for drums and big sounds however it could work.
 
And the most commando way it may work is, download audacity. Load the audio into there. Find a silent-ish part of the audio. Highlight it, go to noise removal. Learn the noise. Go back into and do gentle reductions until you reduce the ambience enough. 
 
Stick a Gate plug-in at the back of it to reduce any remaining "room". Also using an EQ to roll off any unused frequency space eg. from 8Khz onward with a 24dB slope.
 
I hope that helps.
 
 

@interpolatet : Thx for the reply ! Since there are 100`s of audio files, loading them into audacity ( i did all the recording with it), would take me probably weeks. But i saw that SPL De-Verb has a 14 day full working demo. I`m more or less finished with the audio drama, so loading De- Verb on the voice bus hopefully does the job.
I played a bit with a noise gate and a transient, and the result was also acceptable.

Since my last answer I have discovered a couple of plug-ins Waves NS1 and Izotope RX Advanced has an ambience reduction tool (spectral editor).