Include Page Number in Abstract

Add \thispagestyle{plain} immediately after starting your abstract environment. (In the report class, at the begin of the abstract environment, \titlepage is called internally by default, which sets \thispagestyle{empty}.)

EDIT: If you want to switch to arabic page numbering for the rest of your paper, consider to use the book class instead of report and to use its \frontmatter and \mainmatter commands. You may emulate the behaviour of report with \documentclass[oneside]{book}. (Note that the book class doesn't provide an abstract environment; however, an unnumbered frontmatter chapter is quite suited for an abstract of a longer work.)