Data Deletions

Quick question about deleting data from SQL Server.

We have a table that gets quite a bit of activity with an attribute of
type text (inserts that store new text entries of 50-200k apiece).
Older rows aren't needed so we have a process that deletes rows more
than 30 days old (using delete statements).

When these rows are deleted, is the memory consumed by these
automatically recovered? Or is there some process that must be
performed to recover the space? What about the transaction log? Does
that grow with each deletion? When do transaction logs get reset?

Thanks,
John