Hi Muffin, I posted the 1901 for you yesterday, I have rechecked and all details are as posted, all there, all single.
When I rechecked, on previous page at same address 42 Albert Street, same address as parents 1901
John Rogers 24, hd, m, family gardner, cardiff, Glam
Louisa Rogers, 23, wife, somerset
Lily Dau 5 cardiff
Alice, 3, dau, cardiff
Marriages Sep 1896
Sutton Louisa Cardiff 11a 436
ROGERS John Cardiff 11a 436
So it seems that Louisa is down twice at same address. It could be that parents included them as always, or perhaps were losing it a bit. Or enumerator did not know his job...
It seems the three were married and are recorded twice in the 1901. Once with parents as single, the other with married partners.

Maud is with husband Francis Fisher 1901
RG13 Piece: 4977 Folio 64 Page 2
22 Lillenny? Street, Cardiff
Francis L Fisher 20 dock lab, Alridge Lane (N26)
Maud E Fisher 19 wife, Bath, Somerset
Francis H Fisher 1 son Cardiff
Maud E Fisher dau, 9 months Cardiff
Cas