When teaching children how to solve word problems, many teachers model how to solve the problem on the board with a diagram and think-aloud (going through each step/thought process). A great digital tool to use is a site called Thinking Blocks. It allows teachers to model how to draw/label a diagram for addition, subtraction, multiplication, and division. As the website states, word problems are easier to solve when you build a model first.
Rounding is a difficult concept to master for students who do not have strong number sense. In our classroom, we use wipe-off numbers lines for students who have a difficult time visualizing how a number fits within a framework of different numbers. The number lines that skip-count by 10s and 100s are used when my students are rounding to the 10s or 100s.The last number line, featured blank, is used for students who want to make their own number line to help them round.