In the New 52 (Teen Titans #6, 2015) when Raven cast a spell, she uses some strange language, but I can't find out what this language means.
I don't think this is another language. The script doesn't look like any real writing system I've seen. It's more likely a custom magical-looking font, maybe disguising some English text. Usually four small words wouldn't be enough of a sample size to do any deciphering, but this panel gives us a clue: Someone on the far right points out (in case we couldn't figure it out?) that Raven is casting a spell!
The last word that Raven utters is five letters long, and all the letters are different, except for the last two. Just like the word spell! Let's see if this gets us anywhere.
If we assign arbitrary letters of our Roman alphabet to Raven's utterance, we can read it as:
ABCB DEFBG H GIBJJ
If we hypothesize that the last word is a cipher of "SPELL" then the whole thing looks like...
ABCB DEFBG H GIBJJ E E ES SPELL
If the single-letter word is English, it must be "I" or "A." And "I" doesn't really make sense in this context...
ABCB DEFBG H GIBJJ E E ES A SPELL
This is actually looking really good. The "ES" at the end of the second word indicates a verb in a place where we'd expect a verb. The first word "_E_E" could be a lot of things, though. Let's see...
ABCB DEFBG H GIBJJ HERE ES A SPELL
And this matches a common English formation, yielding something that totally matches what Raven is doing in this context:
ABCB DEFBG H GIBJJ HERE COMES A SPELL !!
Further evidence for this interpretation: The "S" glyph looks like an S. The "C" glyph looks like a C. The "P" glyph looks like an upside-down P!
After all that cryptographic analysis, @Moyli supplied some far more conclusive evidence by discovering the actual font used, "Gobbledygook," which you can test out here and confirm that the actual letters on the page are indeed "here comes a spell!!"