Í used www.genlias.nl and I saw on the death-record of Roelof that they used the name Aaltje Bakker as his mother's name but searching further I think they made a mistake and used the name of his former mother-in-law's name.
I think that his mother's name is Roelofje Roelofs.
Confusing but the name Labrie is also written as Labri, Labrij. Cornelis also as Kornelis.
The same with Roelofs wife surname Boxen, also Boxem, Boijem.
So on Genlias start with the parameter for names on "begins " and fil in Lab and Roe and you find more childeren etc.
For the records we use Familysearch but go first to www.genver.nl
For example the attachments of the marriage-record of Roelof go to , on Genver, Overijssel,Zwartsluis, huw.-bijlagen 1823-1832 (image 1068 untill 1073 )
On the death-record of Roelofje d.1815 no names of her parents and the death-record of Cornelis I haven't found yet.