。
There are lots of long, straight roads in Hokkaido.
Literal
Hokkaido [in-には] long-and straight road [subject-が] many [explanatory-んだ].
長くて is the te-form of 長い, used to link two i-adjectives ('long and straight'). まっすぐ ('straight') is a na-adjective-ish that can modify nouns directly. The characteristically Hokkaido feature of long straight roads — contrasting with the winding narrow streets of the rest of Japan.