A Number class provided by roundup is a number of type Real. So, it
always come with a decimal part. But there is a rare case when Numbers
field used to store real type values. 

In common case there is a need to truncate decimal part to show it as
integer (at least, with Jinja engine).

So, i propose a patch (attached) to make Integer class available.
You can add fields of type Integer in common way in schema.py:

...=Class(...
value=Integer(),
...)

Needs testing.