Are the roads included in the places where prayer is forbidden and what is the proof for this? Also, how do we get a combined understanding between this and the prophet's statement: "The earth was made a Masjid (place of prayer) and a means of purification for me."
Yes, the middle part of the road where the people walk is included in the seven places that are prohibited for offering prayer, as has been reported from the prophet. Ibn Majah recorded in his Sunan from Ibn Umar, may Allah be pleased with him that the prophet said:
"It is not permissible to offer the prayer in seven places: the top of the house of Allah (the Ka'bah), the graveyards, the dung heaps (i.e.,waste areas), the slaughter houses, the restroom, the resting places of camels and the middle of the road." (At-Tirmithi no.346 and Ibn Majah no.747
Even though the chain of narration of this hadith is weak, there are other Hadiths that have been reported that explain the places where it is prohibited to offer prayer.
These hadiths are combined with the Hadith of Jabir bin Abdullah, may Allah be pleased with them both, who said that the messenger of Allah said:
"The earth was made a Masjid (place of prayer) and a means of purification for me. So, any man whom (the time of) the prayer catches, let him pray wherever it catches him." (Al-Bukhari no.438, Muslim no.521 and Ahmad no. 3:304)
This was recorded by Imam Ahmad, Al-Bukhari and Muslim. The combined understanding is that the Hadith of Jabir, and other Hadiths that allow the prayer in any place, are general, and the Hadiths that prohibit prayer in places where there is a confirmed prohibition concerning them, are specific.
Thus these Hadiths particularize the generality of the Hadiths that allow the prayer in every place. This is an application of the well-known principle when looking at Hadiths together that are apparently contradictory.
However, if there is a need or necessity that calls for offering prayer in a place from among the prohibited places, then it is permissible to do so.
Reference: Permanent Committee for Research and Verdicts; Fatawa Islamiyah, Vol.3, p.g 33,34.