Dear Regilesh,
Thanks for using Aspose.Slides.
Row height depends on the font height, for example, if font height is greater than the row height, then row height will be adjusted accordingly.
The code below has set the font height to 4 and then setting the row height to 100 works quite fine.
To change table height, you should use Table.Height property.
Presentation srcPres = new Presentation();
Slide srcSld = srcPres.GetSlideByPosition(1);
Table tbl=srcSld.Shapes.AddTable(300, 500, 5000, 1, 1, 1);
//set the row height to 100
tbl.SetRowHeight(0, 100);
//change the font height to 4
Aspose.Slides.Cell cl = tbl.GetCell(0, 0);
cl.TextFrame.Paragraphs[0].Portions[0].FontHeight = 4;
//retrieve row height, it is same as we set earlier
int rh = tbl.GetRowHeight(0);