Yes.
In Chapter 33 of AFFC , Jaime discusses the matter with his cousin Ser Daven, who mentions: His wife's with child, did you know?
He also says that she is "fond of Edmure", which Daven finds odd.
In any case, this confirms both of them are still consider married and (oddly enough) still wish to be married.
scifi.stackexchange.com/users/5798/Justin Ethier
Yes, the wedding is presumably still valid... if it was actually consummated (i.e. Edmure and Roslin had sex).
As far as I can recall (and the Wiki of Ice and Fire backs me up), marriage in Westeros generally requires the two participants to willingly exchange vows, and then consummate the marriage in bed.
A wedding that has not been consummated can be annulled.
I believe this came up with the marriage of Tyrion to Sansa, since he did not force her to consummate it.
However, failure to consummate doesn't mean they aren't married, just that it can be dissolved.
They clearly were brought up for the bedding ceremony, although I don't recall if there was any indication of what happened after they were stripped and thrown in the bedroom.
I recall that Roslin was distraught:
Poor Roslin's smile had a fixed quality to it, as if someone had sewn it onto her face. and 'To bed!
To bed!
*
To bed with them!'
Roslin had gone white.
Catelyn wondered whether it was the prospect of losing her maidenhead that frightened the girl, or the bedding itself....
Catelyn felt sorry for the girl.
Most brides tried to return the banter, or at least pretended to enjoy it, but Roslin was stiff with terror, clutching the Greatjon as if she feared he might drop her.
She's crying too, Catelyn realized..." But fear of her grandfather would likely keep her from revealing anything to Edmure, and he certainly seemed willing, and unaware.
So it seems likely the marriage was consummated.
The vows were certainly exchanged, and exchanged willingly, so the circumstances of the later wedding... "activities"... do not change the status of the marriage.
Only Edmure's opinion of his new family.
scifi.stackexchange.com/users/1359/Beofett
Yes they are still married and they have consummated the marriage.
In A Feast for Crows, in one the chapters of Jaime's (not sure which one -- I think chapter 33)
Edmure says that he was consummating the marriage during the murders of the Red Wedding (seksy).
He said that the Freys had posted musicians right outside of their room so that they won't hear what is happening in the castle.
It is even mentioned that Edmure got his wife with child and Jaime
said that if it was born, he would send it to him in a catapult.
scifi.stackexchange.com/users/19374/Shevliaskovic
You ask if the marriage is still valid.
I ask... why wouldn't it be?
There is nothing to indicate that Roslin knew about what was going to happen or was forced into the wedding.
Likewise, Edmure consented to the marriage out of his own free will.
The matter of them consummating or not doesn't even affect if the marriage is valid, just if it can be annulled.
Sure, it is quite possible that Edmure does not want to be married to Roslin anymore after the atrocity that her family committed, but that doesn't mean the marriage isn't considered valid.
However!
There might be things we do not know.
Westeros is very much a country that relies on "old laws" like the guest right.
There may very well be a law that states that a marriage may be annulled if it turns out that the bride's family has committed heinous crimes, but that is not something we know from reading the books.
So yes, as far as we know, the marriage is still valid and can't be annulled.
scifi.stackexchange.com/users/22803/Theik
Yes, they have consummated the marriage, Chapter 33, AFFC: " ...
The Blackfish pays his mummer's show no mind, so come evenfall Lord Edbure is taken down again.
His wife's with child, did you know?"
He hadn't.
"Edmure bedded her, after the Red Wedding?" "He was bedding her during the Red Wedding.
Roslin's a pretty little thing, hardly stoatish at all.
And fond of Edmure, queerly.
Perwyn tells me she's praying for a girl."
Jaime considered that for a moment.
"Once Edmure's son is born, Lord Walder will have no more need of Edmure."
scifi.stackexchange.com/users/30751/roymeo
Given that...    The Freys slaughtered Edmure's sister and nephew, and many men and women loyal to the Starks and the Tullys, and given that the Red Wedding was a hideous farce of a wedding created not for political ties but for the purposes of regicide and mass slaughter...   Do we still consider Edmure's marriage to Roslin valid? After all, I'm not sure a man in his right mind would  want  to be married to the granddaughter of the architect of the Red Wedding.
Are Edmure and Roslin still considered married?
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scifi.stackexchange.com/users/25915/Lou
The wedding is presumed to be valid and to have been consummated. Edmure and Roslyn are indeed married.
Edmure and Roslyn are indeed married.