According to my book of Freetown Vital Records, compiled by Helen Gurney Thomas, there were 3 Deborah Rider/Ryder listings.

Rider/Ryder
Deborah & Trace Brown, int. 25 Sep 1831.

Deborah, 2d & Macomber A. Rounseville, 1st int. 3 Dec. 1843, 2d int. 6 Jul 1846.

Deborah, 60 & Daniel H. Howland, 70 wid, s. Joseph, both res. of F, 15 Apr 1848.

Now the 2nd one which is one you were asking about is very interesting, under deaths in Freetown is listed -
"______ s. Macomber Rounseville & Deborah Rider, 2d ... 7 Mar 1845"

This child is also under births. The only other birth to them is -
_____ , d. Macomber (molder)& Dedorah (b Roch) ... 27 Aug 1849.

Since your Deborah is called 2d in marriage record I'm guessing her mom was Deborah also. Maybe even the 60 year old who married Daniel Howland ?? Something to check out at least. You may have the wrong Deborah as under marriage -
Brailey/Braley/Brayley
Silas, 21, s. Silas & Esther & Salome Rider, 18, d. Deborah Rider, 24 Sep 1854.

Now this would make Salome born c. 1836, and she is NOT listed as Rounseville. Maybe you Deborah had 1st husband named Rider & that is what the 2d means in her int. above.
I would suggest checking Rider marriages prior to 1836 with wife Deborah.

Not sure if this will help you at all or only confuse the matter even more.

Good Luck & Happy Hunting