Dallas was not in the household in the 1870 census, so is this enumerator error or is he really their son?  Probably the latter because I cannot find a "Dallas" ROSE anywhere else in the 1807 census.
Lafayette's age changes from the 1870 to the 1880 census, so the one born 1868/9 may have died and a second one, born 1870, may have replaced him.

1.  Marriage Record:

2.  1850 Census Every-Name-Index/Images (online at Ancestry.com; Image #108 of 165):  38th District, Mason Co., VA [now WV], Roll M432_959, p. 415B, 753/764, enumerated 4 Sep 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Daniel C Rose	26	M		Labourer		Pa
Mary A    "	22	F				Va
Anna      "	4	F				O
Nancy     "	2	F				Va

3.  1860 Census Index/Images (online at Ancestry.com, Image #25 of 33):  Portland P.O., Lebanon Twp., Meigs Co., OH, Roll M653_1008, p. 303, PN 217, 1604/1563, enumerated 20 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Daniel C Rose	36	M		Farm Laborer		100	Penn
Mary      "	31	F					"
Anna      "	13	F					O
Nancy     "	11	F					Va
Louisa    "	9	F					O
Amanda    "	6	F					"
Martin    "	3	M					Va
Mary      "	2/12	F					O

4 .  1870 Census Every-Name-Index/Images (online at Ancestry.com, Image #14-15 of 30):  Marietta P.O., Marietta Twp., Washington Co., OH, Roll M593_1279, pp. 262B-263A, PN 14-15, 99/99, enumerated 4 Aug 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Rose Daniel C	49	M	W	Farm Hand		100	Penna
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Rose Mary A	43	F	W	Keeping House		300	Penn
____ Ann	23	F	W	Helps Mother			Ohio
____ Nancy	19	F	W	Helps Mother			Ohio
____ Martin	13	M	W	Work on Farm			Ohio
____ Mary J	10	F	W	At School			Ohio
____ Pauline	7	F	W	At School			Ohio
____ George	4	M	W				Ohio
____ Laffeth?	1	M	W				Ohio

5.  1880 Census: Every-Name-Index/Extraction (online at FamilySearch.org); Every-Name-Index/Images (online at Ancestry.com, Image #31 of 34):  Williamstown, Wood Co., WV, Roll T9-1416, p. 327A, PN 31, SD 1, ED 164, enumerated 15 Jun 1880, official enumeration date 1 Jun 1880 (extracted by Diana Gale Matthiesen):

1880:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).

1

2

3

4

5

6

9

10

13

23

24

25

26

8

9

Rose Danil C

W

M

59

/

Farmer

/

PA

NY

NY

____ Mary A

W

F

53

/

Keeping House

PA

PA

PA

____ Pauline

W

F

17

/

At Home

OH

PA

PA

____ George W

W

M

13

/

/

OH

PA

PA

____ Dallas

W

M

12

/

/

WV

PA

PA

____ Lafayette

W

M

10

/

WV

PA

PA

Who is Dallas?  He was not in the household in 1870. 

6.  1890 Census:  the 1890 Census Population Schedules were destroyed.

7.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).